Complete Nutrient Content of Four Species of Commercially Available Feeder Insects Fed Enhanced Diets During Growth

Abstract

Commercially raised feeder insects used to feed captive insectivores are a good source of many nutrients but are deficient in several key nutrients. Current methods used to supplement insects include dusting and gut-loading. Here, we report on the nutrient composition of four species of commercially raised feeder insects fed a special diet to enhance their nutrient content. Crickets, mealworms, superworms, and waxworms were analyzed for moisture, crude protein, fat, ash, acid detergent fiber, total dietary fiber, minerals, amino acids, fatty acids, vitamins, taurine, carotenoids, inositol, and cholesterol. All four species contained enhanced levels of vitamin E and omega 3 fatty acids when compared to previously published data for these species. Crickets, superworms, and mealworms contained β-carotene although using standard conversion factors only crickets and superworms would likely contain sufficient vitamin A activity for most species of insectivores. Waxworms did not contain any detectable β-carotene but did contain zeaxanthin which they likely converted from dietary β-carotene. All four species contained significant amounts of both inositol and cholesterol. Like previous reports all insects were a poor source of calcium and only superworms contained vitamin D above the limit of detection. When compared to the nutrient requirements as established by the NRC for growing rats or poultry, these species were good sources of most other nutrients although the high fat and low moisture content of both waxworms and superworms means when corrected for energy density these two species were deficient in more nutrients than crickets or mealworms. These data show the value of modifying the diet of commercially available insects as they are growing to enhance their nutrient content. They also suggest that for most insectivores properly supplemented lower fat insects such as crickets, or smaller mealworms should form the bulk of the diet.

Full text

RESEARCH ARTICLE
Complete Nutrient Content of Four Species of
Commercially Available Feeder Insects Fed Enhanced
Diets During Growth
Mark D. Finke*
Rio Verde, Arizona
Commercially raised feeder insects used to feed captive insectivores are a good source of many nutrients but are deficient in
several key nutrients. Current methods used to supplement insects include dusting and gut-loading. Here, we report on the
nutrient composition of four species of commercially raised feeder insects fed a special diet to enhance their nutrient content.
Crickets, mealworms, superworms, and waxworms were analyzed for moisture, crude protein, fat, ash, acid detergent fiber,
total dietary fiber, minerals, amino acids, fatty acids, vitamins, taurine, carotenoids, inositol, and cholesterol. All four species
contained enhanced levels of vitamin E and omega 3 fatty acids when compared to previously published data for these species.
Crickets, superworms, and mealworms contained b-carotene although using standard conversion factors only crickets and
superworms would likely contain sufficient vitamin A activity for most species of insectivores. Waxworms did not contain
any detectable b-carotene but did contain zeaxanthin which they likely converted from dietary b-carotene. All four species
contained significant amounts of both inositol and cholesterol. Like previous reports all insects were a poor source of calcium
and only superworms contained vitamin D above the limit of detection. When compared to the nutrient requirements as
established by the NRC for growing rats or poultry, these species were good sources of most other nutrients although the high
fat and low moisture content of both waxworms and superworms means when corrected for energy density these two species
were deficient in more nutrients than crickets or mealworms. These data show the value of modifying the diet of commercially
available insects as they are growing to enhance their nutrient content. They also suggest that for most insectivores properly
supplemented lower fat insects such as crickets, or smaller mealworms should form the bulk of the diet. Zoo Biol. 9999:1–11,
2015. © 2015 The Authors. Zoo Biology published by Wiley Periodicals, Inc.
Keywords: insects; b-carotene; fatty acids; vitamin E; minerals; vitamins; amino acids
INTRODUCTION
Nutrient analysis of commercially bred insects is now
available because of their role as food for captive
insectivores kept in zoos or as pets by hobbyists [Jones
et al., 1971; Martin et al., 1976; Pennino et al., 1991; Barker
et al., 1998; Finke, 2002; Oonincx and Dierenfeld, 2011;
Finke, 2013]. Nutritional analysis of commercially bred
insects suggests they are excellent sources of most nutrients
including minerals, amino acids, fatty acids, and vitamins.
Nutrients which appear to be low across most species of
commercially bred insects include calcium, vitamins A, D, E,
thiamin, and omega-3 fatty acids. Additionally some other
nutrient concentrations like pyridoxine and several minerals
are low in certain species of commercially breed insects. This
is supported by reports of proven or suspected nutrient
deficiencies in captive bred insectivores including calcium,
vitamin A, vitamin D, and thiamin. [Ferguson et al., 1996;
Miller et al., 2001; Pessier et al., 2005; Crawshaw, 2008;
Hoby et al., 2010; Oonincx et al., 2010; Feldman et al.,
2011]. Recently, it has been suggested that in addition to
more traditional ways of supplementing the base nutrient
content of insects such as dusting and gut-loading, their
Conflict of interest: None.
Correspondence to: Mark D. Finke, 17028 E Wildcat Tr., Rio Verde
85263, Arizona.
E-mail: markfinke@desertinet.com
Received 24 June 2015; Revised 19 August 2015; Accepted 31 August 2015
This is an open access article under the terms of the Creative Commons
Attribution License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited.
DOI: 10.1002/zoo.21246
Published online XX Month Year in Wiley Online Library
(wileyonlinelibrary.com).
© 2015 The Authors. Zoo Biology published by Wiley Periodicals, Inc.
Zoo Biology 9999 : 1–11 (2015)

nutritional content might be improved by altering the diet
used by the supplier to grow the insect. [Ferrie et al., 2014;
Livingston et al., 2014]. So, the purpose of this study is to
provide a nutrient analysis of four species of commercially
bred insects fed a special feed designed to enhance their
nutrient content. While the focus of this study is on the
nutrients that were targeted for dietary modification
(b-carotene, vitamin E, omega-3 fatty acids [all species],
and thiamin [crickets and superworms only]) the insects were
analyzed for all known nutrients for comparison to
previously published data for these species.
METHODS
Cricket (late instar Acheta domestica nymphs), meal-
worms (late instar larva of the beetle Tenebrio molitor)
superworms (late instar larva of the beetle Zophobas mori),
and waxworms (late instar larva of the moth Galleria
mellonela) were obtained from Timberline Live Pet Foods
(Marion, IL 62959). Insects fed special diets and marketed for
enhanced nutrient content (Vita-bugs
1
) were used in this
analysis. For crickets and superworms the base diet was
modified to increase omega-3 fatty acids (via flaxseed, canola
oil, and fish oil), lutein (via corn gluten meal and a yellow
carotenoids supplement –Oro Glo
TM
) and vitamin E, thiamin
and b-carotene using commercial supplements. For meal-
worms the base diet was modified to increase omega-3 fatty
acids (via canola oil and fish oil), and vitamin E and b-
carotene using commercial supplements. For waxworms the
base diet was modified to increase omega-3 fatty acids (via
flaxseed, canola oil, and fish oil), and vitamin E and
b-carotene using commercial supplements. Twenty five
individuals of each species were weighed to the nearest mg to
determine average weight. For each species tested approx-
imately 500–800 g of live insects were shipped to a
commercial analytical laboratory (Covance Laboratories,
Madison, Wisconsin 53707) for analysis of moisture, protein,
fat, ash, acid detergent fiber (ADF), total dietary fiber (TDF),
minerals, amino acids, fatty acids, vitamins, cholesterol,
inositol, and selected carotenoids. The insects were shipped
live and kept frozen at 70°C upon receipt until analyzed. All
insects were fasted for approximately 24 hr prior to analysis
to minimize the effects of food retained in the gut. All values
reported are the result of a single analysis and the analytical
methods used to analyze these insect samples are shown in the
appendix. Nitrogen free extract (NFE) was calculated as 100
minus the sum of moisture, crude protein, crude fat, ash, and
ADF. Metabolizable energy (kcal/kg) was calculated using
standard calculations ([g of crude protein 4.0] þ[g of crude
fat 9.0] þ[g of NFE 4.0]). Protein recovery was
calculated as the sum of the amino acids plus taurine divided
by crude protein (nitrogen times 6.25). Fatty acid recovery
was calculated as sum of the fatty acids divided by crude fat.
The nutrient content of these insects was compared with NRC
recommendations for both the laboratory rat (growth) and for
domestic poultry (0–3 week old broiler chickens) [NRC,
1994; NRC, 1995] since these are likely close to true
requirements and can serve as reasonable models for many
captive insectivores. All comparisons were adjusted for
insect energy density (nutrients/1,000 kcals). Detailed
nutrient data on an as is, dry matter and per 1,000 kcal basis
and comparisons to the requirements of the laboratory rat,
broiler chickens, trout, growing dogs, and growing cats are
shown in appendix Tables 1–4 [NRC, 1994; NRC, 1995;
NRC, 2006; NRC, 2011].
RESULTS
Insect weights, proximate analysis, and metabolizable
energy content are shown in Table 1. As expected all four
insect species were fairly high in protein and fat with the
superworms and waxworms containing much more fat than
mealworms and crickets. As a result of the high fat and low
moisture content waxworms contained only 86% of the
protein recommended for broiler chickens. All four species
contained similar levels of fiber as measured by both ADF
and TDF. As expected, the ash content of all four insect
species was low. Energy content (as is) varied widely with
cricket nymphs containing the least amount of energy while
waxworms contained the most.
Mineral analyses are shown in Table 2. All four species
were a poor source of calcium containing less than 50% of
TABLE 1. Average weight and proximate analysis of selected insect species on an as is basis
Crickets Mealworms Superworms Waxworms
Weight (mg/insect) 349 78 558 235
Moisture (g/kg) 725 689 630 641
Crude Protein (g/kg) 165 186 186 144
a
Crude Fat (g/kg) 79 82 14.4 19.4
NFE (g/kg) 1 9 7 2
Total Dietary Fiber (g/kg) 10.9 12.9 14.4 <7.5
Acid Detergent Fiber (g/kg) 17.8 22.3 23.4 15.2
Ash (g/kg) 12.2 11.3 9.3 8.0
Metabolizable Energy (kcal/kg) 1,375 1,520 2,069 2,322
Metabolizable Energy (cal/insect) 480 119 1,154 546
If no superscript is shown the insect meets the requirement of both rats and broiler chickens.
a
Value is 50–100% of the NRC requirements of 0–3 week old broiler chickens.
2Finke
Zoo Biology

the requirements for both rats and poultry. Iron levels met the
requirements established for growing rats in all species
except waxworms but would be considered deficient for
poultry ranging from 17% to 54% of the requirement.
Manganese was low in all species with only crickets meeting
the requirement of the growing rat whereas no insect species
met the requirement of poultry. Only crickets contained
detectable levels of iodine. Other mineral deficiencies
observed were mostly restricted to waxworms and to a
lesser degree superworms as a result of the high fat and
energy content of these two species.
Amino acid analyses are shown in Table 3. These
insects appear to be a good source of most of the essential
amino acids. Both waxworms and superworms contained
only 53% and 74% of the sulfur amino acid (methionine plus
cysteine) requirement of poultry. Only crickets contained
detectable amounts of taurine. When compared to NRC
requirements for rats or poultry the first limiting amino acid
for all four species of insects appears to be the sulfur amino
acids methionine and cystine. Protein recovery for all species
of insects tested was excellent ranging from 95.5% to
103.2%.
Vitamin analyses are shown in Table 4. None of the
insects contained detectable levels of vitamin A/retinol or
vitamin D
3,
and only superworms contained detectable levels
of vitamin D
2
. Vitamin E content was high ranging from 53.7
to 163.0 IU vitamin E/kg. Only crickets contained vitamin K
above the threshold for detection (50 mg/kg). All insects
tested contained substantial quantities of most of the B-
vitamins and choline, although lower levels of both thiamin
(50–100% of the requirements) and vitamin B
12
(<50% of
the requirements) were found in mealworms, superworms,
and waxworms. Only crickets contained sufficient thiamin
and vitamin B
12
to meet the requirements of both rats and
poultry. All species contained significant quantities of
inositol.
Table 5 shows the fatty acid composition of the various
insect species. All insects contained adequate levels of the
essential fatty acid linoleic acid (18:2 n-6) to meet NRC
recommendations for rats. In addition, all insects also
TABLE 2. Mineral content (mg/kg) of selected insect species on
an as is basis
Mineral Crickets Mealworms Superworms Waxworms
Calcium 366
a,c
156
a,c
262
a,c
203
a,c
Phosphorus 2,190 2,640 2,090
d
1,930
d
Magnesium 193
d
620 435 266
b,d
Sodium 1,110 225
c
385
c
<123
a,c
Potassium 2,850 3,350 2,860 2,310
Chloride 2,210 1,760 1,630 760
d
Iron 17.5
d
20.7
d
19.9
c
9.6
a,c
Zinc 54.3 49.5 30.2 25.9
d
Copper 6.3 8.3 3.6
d
3.3
d
Manganese 8.7
c
3.2
b,c
3.7
b,c
2.7
a,c
Iodine 0.145 <0.10
a,c
<0.10
a,c
<0.10
a,c
Selenium 0.133 0.123 0.103 0.177
a
Value is <50% of the NRC requirement of rats for growth.
b
Value is 50–100% of the NRC requirement of rats for growth.
c
Value is <50% of the NRC requirements of 0–3 week old broiler
chickens.
d
Value is 50–100% of the NRC requirements of 0–3 week old
broiler chickens.
TABLE 3. Amino acid content (g/kg) of selected insect species on an as is basis
Amino acid Crickets Mealworms Superworms Waxworms
Alanine 15.0 16.4 14.4 11.8
Arginine 13.6 13.8 12.9 11.8
Aspartic acid 13.0 15.2 16.2 14.3
Cystine 1.61 1.63 1.75 1.09
Glycine 8.83 10.0 9.29 7.94
Glutamic acid 18.9 21.3 24.4 18.2
Histidine 3.64 5.59 5.92 3.17
Isoleucine 6.65 8.35 8.81 6.58
Leucine 11.7 14.0 13.6 10.8
Lysine 9.56 10.7 10.7 8.56
Methionine 2.74 2.55 2.55
a,b
2.40
a,b
Phenylalanine 5.87 6.54 7.40 5.80
Proline 9.86 12.8 10.6 10.4
Serine 6.67 8.60 8.12 9.48
Threonine 6.21 7.57 7.47 5.99
Tryptophan 1.44 2.16 2.03 1.63
Tyrosine 10.7 11.9 13.1 9.10
Valine 9.84 12.8 12.3 9.53
Taurine 0.18 <0.1 <0.1 <0.1
Methionine þCystine 4.35 4.18
b
4.30
a,b
3.49
a,b
Phenylalanine þTyrosine 16.6 18.4 20.5 14.9
Protein Recovery (as is) 95.5% 97.8% 97.6% 103.2%
a
Value is 50–100% of the NRC requirement of rats for growth.
b
Value is 50–100% of the NRC requirements of 0–3 week old broiler chickens.
Complete Nutrient Content of Four Species of Feeder Insects 3
Zoo Biology

contained significant levels of linolenic acid (18:3 n-3) and
lesser amounts of eicosapentaenoice acid (20:5 n-3). The
three dominant fatty acids in all four species were oleic acid
(18:1), palmitic acid (16:0), and linoleic acid (18:2). Fatty
acid recovery was good ranging from 84.8% to 87.9%.
Cholesterol levels ranged from 513 to 985 mg/kg.
Selected carotenoids are shown in Table 6. Crickets,
mealworms, and superworms all contained b-carotene
TABLE 4. Vitamin, choline, and inositol content of selected insect species on an as is basis
Vitamin Crickets Mealworms Superworms Waxworms
Vitamin A (IU/kg - from retinol) <1,000
a,c
<1,000
a,c
<1,000
a,c
<1,000
a,c
Vitamin D
2
(IU/kg) <40
a
<40
a
531 <40
a
Vitamin D
3
(IU/kg) <40
a,c
<40
a,c
<40
a,c
<40
a,c
Vitamin E (IU/kg) 53.7 36.2 163.0 63.3
Vitamin K (mg/kg) 78.4 <50
a,c
<50
a,c
<50
a,c
Vitamin C (mg/kg) 92.0 99.0 101.0 90.0
Thiamin (mg/kg) 2.0 1.1
b
1.7
b
1.2
b,d
Riboflavin (mg/kg) 16.6 8.7 11.2 9.3
Pantothenic Acid (mg/kg) 20.3 15.6 7.0 32.8
Niacin (mg/kg) 29.5 46.5 35.3 33.6
Pyridoxine (mg/kg) 2.13 6.90 3.55 1.74
a,d
Folic Acid (mg/kg) 1.07 1.55 0.64 0.61
Biotin (mg/kg) 0.21 0.43 0.38 0.29
Vitamin B
12
(mg/kg) 193.0 1.3
a,c
9.9
a
<1.2
a,c
Choline (mg/kg) 1,020 1,410 1,240 1,550
Inositol (mg/kg) 345 267 223 236
a
Value is <50% of the NRC requirement of rats for growth.
b
Value is 50–100% of the NRC requirement of rats for growth.
c
Value is <50% of the NRC requirements of 0–3 week old broiler chickens.
d
Value is 50–100% of the NRC requirements of 0–3 week old broiler chickens.
TABLE 5. Fatty acid (g/kg) and cholesterol (mg/kg) content of selected insect species on an as is basis
Fatty Acid Crickets Mealworms Superworms Waxworms
Caprylic 8:0 <0.07 <0.07 0.71 <0.07
Capric 10:0 <0.07 <0.07 0.13 <0.07
Lauric 12:0 <0.07 0.11 <0.07 <0.07
Myristic 14:0 0.59 1.43 1.67 0.42
Myristoleic 14:1 <0.07 <0.07 <0.07 <0.07
Pentadecanoic 15:0 0.10 0.16 0.37 <0.07
Pentadecenoic 15:1 <0.07 <0.07 <0.07 <0.07
Palmitic 16:0 17.2 12.3 35.9 59.7
Palmitoleic 16:1 0.85 0.84 1.37 3.95
Heptadecanoic 17:0 0.19 0.22 0.75 0.09
Heptadecenoic 17:1 <0.07 <0.07 <0.07 <0.07
Stearic 18:0 6.54 2.56 11.5 4.09
Oleic 18:1 16.4 27.3 42.8 79.0
Linoleic 18:2 20.7 24.3 26.4 17.6
Gamma Linoleic 18:3 <0.07 <0.07 <0.07 <0.07
Linolenic 18:3 3.49 1.03 3.76 2.91
Octadecatetraenoic 18:4 <0.07 <0.07 0.09 0.19
Arachidic 20:0 0.19 0.18 0.29 0.16
Eicosenoic 20:1 0.14 0.19 0.18 0.10
Eicosadienoic 20:2 <0.07 <0.07 0.08 0.12
Eicosatienoic 20:3 <0.07 <0.07 <0.07 <0.07
Arachidonic 20:4 0.14 <0.07 0.09 <0.07
Eicosapentaenoic 20:5 0.44 0.22 0.34 0.31
Benhenic 22:0 <0.07 <0.07 0.12 0.08
Erucic 22:1 <0.07 <0.07 <0.07 <0.07
Docosapentaenoic 22:5 <0.07 <0.07 <0.07 <0.07
Docosahexaenoic 22:6 <0.07 <0.07 <0.07 <0.07
Lignoceric 24:0 <0.07 <0.07 <0.07 <0.07
Cholesterol 985 513 450 753
Fat Recovery (as is) 84.8% 86.4% 87.9% 87.0%
4Finke
Zoo Biology

although levels were much lower in mealworms. Lutein was
detected in crickets, superworms, and waxworms but not
mealworms. Only waxworms contained detectable levels of
zeaxanthin.
DISCUSSION
The proximate analysis for crickets, mealworms,
superworms, and waxworms are similar to previous reports
in the literature for these species [Jones et al., 1971; Martin
et al., 1976; Pennino et al., 1991; Barker et al., 1998; Finke,
2002]. Although the mealworms analyzed in this study
contain 39% less fat than previously reported [Finke,
2002] that is likely a result of their smaller size (78 vs.
126 mg) as lipid content increases with increasing size/age in
mealworm larvae [Finkel, 1948]. Although both acid
detergent fiber (ADF) and neutral detergent fiber (NDF)
have previously been reported for these species this is the
first report of total dietary fiber for commercial feeder insects
[Pennino et al., 1991; Barker et al., 1998; Finke, 2002].
The low calcium content of these four species of
insects is similar to previous reports and is consistent with
most other published data for feeder insects [Jones et al.,
1971; Martin et al., 1976; Barker et al., 1998; Finke, 2002;
Oonincx and Dierenfeld, 2011; Finke, 2013]. In this study,
calcium levels in these four species were only 7–21% and 3–
9% of the requirements for rats and poultry respectively.
Phosphorus contents were much higher than calcium
levels in all species and are similar to those reported
previously [Jones et al., 1971; Martin et al., 1976; Barker
et al., 1998, Finke, 2002]. Both superworms and waxworms
contained insufficient phosphorus to meet the requirements
of poultry (72% and 59% respectively) but levels were
adequate for growing rats. Phosphorus from insects is likely
to be readily available [Dashefsky et al., 1976] which may
compensate for the slightly low levels.
Magnesium content of these species of insects is in
general similar to that reported [Martin et al., 1976; Barker
et al., 1998; Finke, 2002] although the crickets contained
only 58% (per 1,000 kcals) that previously seen for both
smaller cricket nymphs and adult crickets [Finke, 2002].
Sodium, potassium, and chloride levels reported for
these four species are similar to those previously reported
although the value for sodium in mealworms is only 57% that
previously seen [Jones et al., 1971; Martin et al., 1976; Finke,
2002]. Only crickets contained sufficient sodium, potassium,
and chloride to meet the requirements of both rats and
poultry. Sodium was below the detection limits in waxworms
which is in-line with previous information for waxworms
and consistent with reports for wild Lepidoptera (both pupae
and adults) [Studier et al., 1991; Studier and Sevick, 1992;
Finke, 2002].
Levels of iron, zinc, copper, and manganese were
variable but all values were similar to those previously
reported for these four species of insects [Martin et al., 1976;
Barker et al., 1998; Finke, 2002]. Crickets, mealworms, and
superworms met the iron requirements for rats, but were low
for poultry (51%, 54%, and 38% the requirement respec-
tively). Waxworms would be considered deficient for both
rats and poultry (47% and 17% of the requirements
respectively). For manganese only crickets met the require-
ment for rats (250%) whereas levels were below the rat’s
requirement for mealworms, superworms, and waxworms
(84%, 70%, and 45% of the requirement respectively). None
of the four species met the manganese requirements for
poultry with values ranging from 8% to 42% of the
requirement. Zinc and copper were adequate in all species
for both rats and poultry except for waxworms where both
zinc and copper were only 89% and 70% of the requirements
for poultry respectively. Iodine was only detected in crickets,
and levels were sufficient to meet the requirements of both
rats (278% of the requirement) and poultry (121% of the
requirement). This pattern is similar to that previously
observed although in that report mealworms also contained
iodine at relatively low levels [Finke, 2002]. All four species
contained sufficient selenium to meet the requirements of
both rats and poultry. Although the insects analyzed in this
report were “fasted,”mineral composition in general, is
probably a function of the food sources of the insect, both the
minerals absorbed from the diet as well as that remaining in
the gastrointestinal tract [Finke, 2015; Oonincx and van der
Poel, 2010].
The amino acid patterns reported here are consistent
with the amino acid profiles previously reported for these
species [Finke, 2002; Finke, 2007; Bednarov et al., 2014].
The analytical data suggests that for insects, total sulfur
amino acids are first limiting when used to feed rats. Taurine
levels in crickets seen here are similar to those previously
seen in crickets [Finke, 2002] and in wild grasshoppers
TABLE 6. Carotenoid content of selected insect species on an as is basis
Crickets Mealworms Superworms Waxworms
b-Carotene
mg/kg 2.72 0.076 1.99 <0.20
IU Vitamin A/kg 4,533 126
a,b
3,317 <333
a,b
Lutein (mg/kg) 0.204 <0.20 0.284 1.12
Zeaxanthin (mg/kg) <0.20 <0.20 <0.20 0.594
a
Value is <50% of the NRC requirement of rats for growth.
b
Value is <50% of the NRC requirements of 0–3 week old broiler chickens.
Complete Nutrient Content of Four Species of Feeder Insects 5
Zoo Biology

[Finke, 2015]. The lack of taurine in the other three species is
consistent with previous analysis and while taurine was
previously detected in mealworms (80 mg/kg as is) that is
below the detection limit seen in this study [Finke, 2002].
Although there is only limited data available taurine levels
appear to be highly variable in insects and are likely a
function of both the species and life stage [Finke, 2002;
Ramsay and Houston, 2003; Finke, 2013; McCusker et al.,
2014]. In Drosophila melanogaster, taurine levels increased
from approximately 100 mg/kg in larvae to 700–1,100 mg/kg
in adult flies [Massie et al., 1989]. The significance of taurine
for captive insectivores is currently unknown although
several authors have speculated that it may play a role in prey
selection for insectivorous birds feeding their nestlings and
subsequently affect their development and behavior [Ram-
say and Houston, 2003; Arnold et al., 2007].
The excellent recovery of nitrogen/crude protein as
amino acids in all species analyzed here suggests that most of
the nitrogen in these insects is from amino acids and that only
a small amount of the nitrogen is from chitin or other
compounds. This is consistent with previous data for these
species as well as data for other feeder insects [Finke, 2002;
Finke, 2007; Finke, 2013].
No retinol was detected in these four species consistent
with previous reports (the low levels reported by Barker and
Pennino are below the detection limit of this assay) [Jones
et al., 1971; Barker et al., 1998; Pennino et al., 1991; Finke,
2002]. This is consistent with most reports for both
commercially raised and wild insects. Significant levels of
vitamin A have been reported in only a few species of insects
[Pennino et al., 1991; Oyarzun et al., 1996; Finke, 2002].
Locusts fed a grass diet supplemented with wheat bran and
fresh carrots contained significantly more retinol than those
fed only a grass diet, but the retinol levels (110–190 mg
retinol or 366–633 IU Vitamin A/kg dry matter (DM) for all
locusts are well below the requirements of the rat [Oonincx
et al., 2010]. Much like the results observed by Oonincx for
locusts, the retinal content of Vita-bug
1
crickets was about
50% higher than that for crickets fed a regular commercial
cricket diet although both levels were fairly low (320 and
212 IU vitamin A/kg DM respectively) [Finke unpublished
data]. Retinoids are only found in the compound eyes of
insects where they are synthesized from their carotenoid
precursors and the retinoid synthesized (typically either
retinal or 3-OH retinal) is species specific [Smith and
Goldsmith, 1990; Seki et al., 1998]. For that reason it is not
surprising that retinol is rarely detected in whole insects. A
better understanding of the vitamin A content of insects and
the utilization of various insect retinoids and carotenoids as a
source of vitamin A is important as vitamin A deficiency has
been reported in several species of captive insectivores
[Ferguson et al., 1996; Miller et al., 2001; Pessier et al., 2005;
Hoby et al., 2010; Brenes-Soto and Dierenfeld, 2014;
Clugston and Blaner, 2014].
None of the insects sampled contained detectable
levels of Vitamins D
3
and only superworms contained
Vitamin D
2
. Previously vitamin D was not detected in these
species but the threshold for detection was 250 IU/kg where
in this report the detection limit is 80 IU/kg. Similar to these
data Oonincx reported values of 150 IU vitamin D
3
/kg DM
for mealworms [Oonincx et al., 2010]. The values reported
by Oonincx for crickets (934 IU vitamin D
3
/kg DM) were
much higher than the values reported here although these
results may be in part due to the residual food remaining in
the crickets gut [Oonincx et al., 2010]. The vitamin D
requirements for many species can be met though exposure
to specific wavelengths of ultraviolet light so dietary
concentration of vitamin D in feeder insects may be less
critical.
Vitamin E levels are considerably higher than those
previously observed for these species [Pennino et al., 1991;
Barker et al., 1998; Finke, 2002]. Published data shows
vitamin E contents ranging from 9.6 to 26.9 IU/kg (as is) for
crickets, less than 5–33.1 IU/kg (as is) for mealworms,
7.7–13.8 IU/kg (as is) for superworms, and 13–103.9 IU/kg
(as is) for waxworms. In a short-term (7 day) feeding trial
adding vitamin E to the diet of crickets had no effect on
cricket vitamin E content [Pennino et al., 1991]. For
mealworms a short-term (7 day) feeding trial resulted in a
small but significant increase in vitamin E content in
mealworms although it is unclear if these results might
simply be due to the residual food in the gut [Pennino et al.,
1991]. When swine are fed diets with increased levels of
vitamin E during their growth phase elevated amounts of
vitamin E were found in various tissues [Asghar et al., 1991a;
Asghar et al., 1991b].
Although there is relatively little data available, wild
caught insects appear to contain more vitamin E (range
approximately 16–171 IU/kg as is) than typical commercial
feeder insects and the levels are comparable to those
observed here for enhanced feeder insects [Pennino et al.,
1991; Oyarzun et al., 1996; Cerda et al., 2001; Arnold et al.,
2010]. Dierenfeld has reported vitamin E deficiency in zoo
animals and has suggested their diets contain 75–300 IU
vitamin E/kg of diet versus 27 and 10 IU/kg diet suggested by
the NRC for rats and poultry respectively [Dierenfeld, 1989,
1994]. Given that the vitamin E requirements are a function
of both the amount and the type of dietary fat it seems likely
that the current NRC recommendations for rats and poultry
are probably not appropriate for animals fed high fat insects.
There are no previous reports regarding the vitamin K
content of commercial feeder insects. Only crickets
contained detectable levels of vitamin K (78.4 mg/kg). The
detection limit of this assay is high (>50 mg/kg) relative to
the requirements for rats (1 mg/kg diet) or poultry (0.5 mg/kg
diet) so it is unclear as to how to properly interpret these
results relative to the requirements of insectivores.
The vitamin C values reported here are 4-to more than
10 times those previously reported for these four species
[Jones et al., 1971; Finke, 2002]. The reason for this difference
is unknown. Although vitamin C is not a required nutrient for
rats or poultry it is required for guinea pigs, fish, and some
6Finke
Zoo Biology

species of primates [NRC, 1995; NRC, 2011]. The vitamin C
levels reported here would easily meet the recommendations
for trout with values ranging from 775% (waxworms) to
1338% (crickets) of the requirements [NRC, 2011].
For thiamin the large cricket nymphs analyzed in this
report contained 400% and 900% more thiamin than that
previously reported for adult crickets and small nymphs
respectively [Finke, 2002]. Likewise for superworms, values
reported here were 173% higher than those reported
previously [Finke, 2002]. The data is notable as the diets
of both of these two species was modified to include more
thiamin in an effort to increase levels in the insect. In contrast
the thiamin levels in both mealworms and waxworms were
about half that previously reported for these species although
their diet was not modified. The reason for this is currently
unclear although for waxworms the previous analysis were
prepuape and this analysis were larvae. The limit of detection
for this assay is 0.1 mg thiamin/kg and the relative standard
deviation (RSD) is 3.9% in an egg noodle matrix. Thiamin in
feeder insects is of interest since thiamin deficiency has been
reported in Puerto Rican Crested Toads (Bufo lemur)
[Crawshaw, 2008]. In that study, toads recovered when
given a supplement containing calcium, glucose, and thiamin
while those given a supplement containing calcium and
glucose showed no improvement. Presumed thiamin defi-
ciency has also been observed in anoles (Anolis sp) [Feldman
et al., 2011]. Affected anoles recovered within two days after
being injected with a B-vitamin complex. For rats the
thiamin requirement increases with increasing levels of
dietary carbohydrates so for thiamin, rats or poultry may not
be the best model for insectivores consuming a diet
containing little carbohydrates. A thiaminase has been
reported in both Japanese silkworm larvae (Bombyx mori)
and African silkworm pupae (Anaphe spp) [Nishimune et al.,
2000]. The extent to which thiaminases are found in
commercially produced feeder insects and their potential
effect on insectivores is currently unknown.
Values for all of the other B-vitamins were similar to
those previously reported for these species with only a couple
of minor exceptions. Both crickets and superworms
contained more vitamin B
12
(crickets 212% and superworms
135%) than previously reported although no specific
alteration in dietary vitamin B
12
content was made. For
superworms and mealworms pantothenic acid levels were
much lower (superworms 64% and mealworms 41%) than
those reported previously [Finke, 2002]. The reason for these
changes is unclear although it may represent biological
variation, diet variation since natural ingredients are used or
the variation inherent in the assay (the limit of detection for
this assay is 0.4 mg pantothenic acid/kg and the RSD is 4.1%
in an infant formula matrix). These data in conjunction with
previous research suggests that most insect species are a
relatively good source of most B-vitamins although the high
fat content of many insect larvae may mean that when values
are expressed on a per unit energy basis they would be
considered deficient.
There is limited information regarding the choline
content of insects but the data available suggests insects are
rich sources of choline [Finke, 2002, 2013, 2015]. Choline
values reported here range from 316% to 489% and 148%
to 228% of the requirement for rats and poultry
respectively.
There are no previous reports regarding the inositol
content of commercial feeder insects. Although inositol is
not a required nutrient for rats or poultry it is required for fish.
The inositol levels reported here would meet the recom-
mendations for trout with values ranging from 136%
(waxworms) to 335% (crickets) of the requirements [NRC,
2011].
The fatty acid pattern observed for these insects differs
from that previously observed primarily with regard to
linolenic and eicosapentaenoic acid. These data are
consistent with previous literature reports that the fatty
acid content of insects and other monogastric animals like
pigs and poultry can be modified by dietary means.
[Thompson and Barlow, 1972; Cookman et al., 1984; St-
Hilaire et al., 2007]. When expressed as a percentage of the
total fatty acids to compensate for differences in fat content
between studies, insects in this study contained a much
higher proportion of linolenic acid (LNA - 18:3 n-3) than
previously reported (crickets 5.2 versus 1.0%; mealworms
1.5% vs. 1.1%; superworms 3.0% vs. 0.6%, and waxworms
1.7% vs. 1.5%) [Finke, 2002]. Also unlike previous reports
all four species of insects in this study contained
eicosapentaenoic acid (EPA -20:5 n-3) with levels ranging
from 0.2% to 0.7% of the total fatty acids. No docosahex-
aenoic acid (DHA -22:6 n-3) was detected in these insects
even though their diets contains significant quantities of
DHA [Finke unpublished results]. EPA and DHA are not
typically found in terrestrial insects but usually make up a
significant proportion of the total fatty acids in aquatic
insects [Sushchik et al., 2003; Gladyshev et al., 2011;
Zinchenko et al., 2014]. It has been speculated that aquatic
insects may serve an important function in transferring long
chain omega-3 fatty acids from aquatic to terrestrial
environments [Gladyshev et al., 2011]. The increased levels
of both LNA and EPA means the omega-6:omega-3 fatty
acid ratio of these insects is much lower than previously
reported (crickets 5 vs. 39; mealworms 19 vs. 25; super-
worms 6 vs. 30, and waxworms 4 vs. 14) [Finke, 2002]. The
amount of omega-3 fatty acids and the omega-6 to omega-3
ratio has been implicated as being beneficial in a large
number of species due to their role in cell membrane
function, gene expression, and inflammation [Schmitz and
Ecker, 2008]. It is unclear if they might confer similar
benefits to insectivores.
There are no previous reports regarding the cholesterol
content of commercial feeder insects. The values seen here
range from 450 mg/kg (superworms) to 985 mg/kg (crickets).
These values are similar to beef and pork but lower than
poultry (beef 650–750 mg/kg; pork 680–720 mg/kg; poultry
1,040–1,430 mg/kg) [USDA, 2015].
Complete Nutrient Content of Four Species of Feeder Insects 7
Zoo Biology

As shown in Table 6 unlike previous analysis of these
insects, crickets, mealworms, and superworms all contained
b-carotene whereas waxworms did not [Jones et al., 1971;
Finke, 2002]. The reason for the much lower levels of
b-carotene found in mealworms is unclear but may be a
function of their age/size. In Drosophila carotenoid
absorption is facilitated by the NinaD gene which encodes
for a scavenger receptor in the midgut [Voolstra et al., 2006].
In Drosophila NinaD is expressed during late larval stage, so
if mealworms have a similar pattern of expression older
larger mealworm larvae may contain more carotenoids than
younger smaller larvae. The ability of most insectivores to
convert b-carotene to retinol is unknown but the gene
involved in the cleavage of b-carotene into two molecules of
retinal (BCMO1 -b-carotene 15, 150-monooxygenase) is
widely conserved across the animal kingdom including being
detected in several species of insectivores [Sayers et al.,
2009]. Although the efficiency which insectivores might
convert b-carotene to retinol is unknown, using typical
conversion efficiencies of 1 International Unit (IU) of
vitamin A equals 0.6 mgofb-carotene shows crickets,
mealworms, and superworms would contain 4,533, 126, and
3,317 IU of vitamin A respectively. This would be equivalent
to 566%, 14%, and 275% of the vitamin A requirements of
the rat and 703%, 18%, and 342% of the vitamin A
requirements of poultry. In a study with adult cane toads Bufo
marinus, and Cuban tree frogs, Osteopilus septentrionalis,
McComb was unable to show any b-carotene 15,150-
monooxygenase activity in either liver or intestinal tissues
[McComb, 2010]. The tissues in this study were frozen prior
to analysis which may have affected these results.
In a long term feeding trial Oonincx was also able to
enhance the b-carotene content of locusts fed a grass diet
supplemented with wheat bran and fresh carrots compared to
those fed a grass only or grass and wheat bran diet [Oonincx
and van der Poel, 2010]. Since the locusts were not fasted
prior to analysis it is unclear how much of the b-carotene was
incorporated into the tissue of the insects and how much was
simply due to residual food in the gut. The fasted cricket
nymphs analyzed in this study contain 38% more b-carotene
(2.72 vs. 1.97 mg/kg as is) than the gut-loaded locust nymphs
fed grass plus carrots [Oonincx and van der Poel, 2010].
Likewise in a short-term (4 day) feeding trial Oglivy was able
to enhance the carotenoid content of three species of crickets
fed vegetables or a commercial fish food although it appears
most of the enhancement in carotenoid content was a result of
the food retained in the gut [Ogilvy et al., 2011]. In contrast,
the insects in this study were fasted so the enhancement in
b-carotene content is mostly or entirely a result of
incorporation into the insect’s tissues.
The lack of b-carotene in waxworms is likely a result
of conversion of dietary b-carotene to lutein and zeaxanthin.
The chromophore used for visual function by insects is
species specific [Smith and Goldsmith, 1990] with Ortho-
petera (including crickets) and Coleoptera (including the
adults of both mealworms and superworms) using retinal
which can be synthesized by cleaving one molecule of
b-carotene into two molecules of retinal. In contrast,
Lepidoptera (including waxworms) use 3-OH retinal as
their chromophore which is synthesized from zeaxanthin. So
for insect species like waxworms and Drosophila that use
3-OH retinal as their chromophore, dietary b-carotene is first
converted to zeaxanthin which is then used for 3-OH retinal
synthesis [Giovannucci and Stephenson, 1999; Voolstra
et al., 2010]. In insects retinoid synthesis from carotenoid
precursors only occurs in the compound eye so insect larvae,
which lack compound eyes, do not contain retinoids
[Giovannucci and Stephenson, 1999; Voolstra et al.,
2010]. Drosophila accumulate carotenoids during the larval
stage which are then converted to retinoids during the pupal
stage when the compound eyes are formed [Voolstra et al.,
2010; Von Lintig, 2012]. Although retinal has significant
vitamin A activity it is unclear if 3-OH retinal would be a
viable source of vitamin A for insectivores.
In addition to b-carotene, crickets, and superworms
also contained lutein but no zeaxathin whereas waxworms
contained relatively high levels of both lutein and
zeaxanthin. The lutein in crickets and superworms is likely
accumulated from their diet whereas the lutein and
zeaxanthin found in waxworms is likely a combination of
accumulation from the diet and synthesis from dietary
b-carotene. Wild caught insects contain significant amounts
of a variety of carotenoids some of which may serve as a
source of vitamin A for insectivores [Arnold et al., 2010;
Eeva et al., 2010; Helmer et al., 2015; Newbrey et al., 2013].
In addition to their role as precursors for vitamin A
carotenoids may play other important roles in coloration,
immune response, and reproduction in insectivores
[McGraw and Toomey, 2010; Ogilvy et al., 2012; Brenes-
Soto and Dierenfeld, 2014].
CONCLUSIONS
Commercially raised feeder insects are in most cases
likely fed a least-cost diet designed to maximize growth and
reproduction at the lowest cost without regard to the nutrient
content of the feeder insect. These data clearly show that by
changing the diet fed to the insect during growth the nutrient
content of the feeder insect can be substantially altered.
Although not all nutrients (i.e. calcium) can easily be
changed these data suggest that the fatty acid composition,
vitamin E concentrations, carotenoid content, and perhaps
some B-vitamin concentrations in live insects can be altered
by changing the diet fed to the insect while it is actively
growing. In many cases, the nutrient content of insects fed
enhanced diets closely mimics the nutrient content of wild
insects (i.e. vitamin E, carotenoids, and fatty acids profiles).
This technique has the potential to substantially improve the
nutritional value of commercial feeder insects when used as
food for captive insectivores.
These data also provide additional guidance regarding
the use of certain species in captive feeding programs
8Finke
Zoo Biology

[Sincage, 2012]. While high fat insect larvae like waxworms
contain high levels of many nutrients when evaluated on an
as is or DM basis, their high fat content means that when
nutrients are adjusted for energy density they would likely be
deficient in many nutrients. As such they should probably not
form the bulk of a diet for most healthy captive insectivores
unless properly supplemented. High fat/low moisture content
insect larvae may, however, be appropriate as part of a mixed
diet or as the main component of a diet for an unhealthy
animal where the primary nutritional goal is to increase
energy intake. Thus, a mixed diet using a variety of different
insect species that have been properly “gut loaded”or
“dusted”would seem to offer the best hope of providing the
appropriate nutrition to captive insectivores.
ACKNOWLEDGEMENTS
I would like to thank Todd Goodman of Timberline
Fisheries for providing the insects used in this study. The
author developed the diet used for feeding these insects and is
currently a paid consultant for Timberline Live Pet Foods the
provider of Vita-bugs
1
. This paper benefited greatly from
many valuable discussions with Johannes von Lintig
regarding carotenoid and retinoid metabolism in insects.
Also thanks to two unknown reviewers whose many
constructive comments greatly improved this paper.
APPENDIX
Acid Detergent Fiber –United States Department of
Agriculture. 1970. Forage and Fiber Analysis, Handbook
#379.8, United States Department of Agriculture, Wash-
ington D.C.
Amino Acids (including taurine and excluding
tryptophan) –Schuster R. 1988. Determination of amino
acids in biological, pharmaceutical, plant and food samples
by automated precolumn deravitization and HPLC. J
Chromatogr B 431:271-284.
Henderson JW, Ricker RD, Bidlingmeyer, BA, Wood-
ward C. 2000. Rapid, accurate, sensitive and reproducible
HPLC analysis of amino acids using Zorbax Eclipse-AAA
columns and the Agilent 1100 HPLC. Agilent Publication.
Barkholt V, Jensen.AL. 1989. Amino acid analysis:
Determination of cysteine plus half-cystine in proteins after
hydrochloric acid analysis with disulfide compound as
additive. Anal Biochem 177:318-322.
Ash –AOAC. 2005. Official Methods of Analysis of
AOAC International, 18th Ed. Method 923.03, AOAC
International, Gaithersburg, MD.
Biotin –Scheiner J and De Ritter. 1975. Biotin content
of feedstuffs. J Agr Food Chem 23:1157-1162.
Carnitine –Starkey DE, Denison, JE, Seipelt CT,
Jacobs WA. 2008. Single-Laboratory Validation of a Liquid
Chromatographic/Tandem Mass Spectrometric Method for
the Determination of Free and Total Carnitine in Infant
Formula and Raw Ingredients J AOAC Int 91:130-142.
Carotenoids –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 941.15,
AOAC International, Gaithersburg, MD.
Chloride –AOAC. 2005. Official Methods of Analysis
of AOAC International, 18th Ed. Methods 963.05, 969.10
and 971.27, AOAC International, Gaithersburg, MD.
Cholesterol –AOAC 2005. Official Methods of
Analysis of AOAC International, 18th Ed., Method
994.10. (Modified), AOAC International, Gaithersburg, MD.
Choline –AOAC. 2005. Official Methods of Analysis
of AOAC International, 18th Ed. Method 999.14, AOAC
International, Gaithersburg, MD.
Crude Fat –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Methods
960.39 and 948.22, AOAC International, Gaithersburg, MD.
Crude Protein –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 968.06
and 992.15, AOAC International, Gaithersburg, MD.
Fatty Acids –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 996.06,
AOAC International, Gaithersburg, MD.
Folic Acid –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 960.46
and 992.05, AOAC International, Gaithersburg, MD.
Inositol –Tagliaferri EG, Bonetti, G, Blake, CJ. 2000.
Ion Chromatographic Determination of inositol in infant
formulae and clinical products for enteral feeding. J
Chromatogr A. 879:129-135.
Iodine –AOAC. 2000. Official Methods of Analysis of
AOAC International, 17th Ed. Method 932.21, AOAC
International, Gaithersburg, MD.
Minerals (except chloride, iodine and selenium) –
AOAC. 2005. Official Methods of Analysis of AOAC
International, 18th Ed. Method 984.27 and 985.01, AOAC
International, Gaithersburg, MD.
Moisture –AOAC. 2005. Official Methods of Analysis
of AOAC International, 18th Ed. Methods 925.09 and
926.08, AOAC International, Gaithersburg, MD.
Niacin –AOAC. 2005. Official Methods of Analysis of
AOAC International, 18th Ed. Method 944.13 and 960.46,
AOAC International, Gaithersburg, MD.
Pantothenic Acid –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 945.74
and 960.46, AOAC International, Gaithersburg, MD.
Pyridoxine –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 961.15,
AOAC International, Gaithersburg, MD.
Riboflavin –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Methods
940.33 and 960.46, AOAC International, Gaithersburg, MD.
Selenium –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 986.15
and 996.17, AOAC International, Gaithersburg, MD.
Total Dietary Fiber –AOAC 2005. Official Methods of
Analysis of AOAC International 18th Ed., Method 991.43,
AOAC International, Gaithersburg, MD.
Complete Nutrient Content of Four Species of Feeder Insects 9
Zoo Biology

Thiamin –AOAC. 2005. Official Methods of Analysis
of AOAC International, 18th Ed. Methods 942.23, 953.17
and 957.17, AOAC International, Gaithersburg, MD.
Tryptophan –AOAC. 1995. Official Methods of
Analysis of AOAC International, 16th Ed. Method 982.20,
AOAC International, Arlington, VA.
Vitamin A –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 974.29,
992.04 and 992.06, AOAC International, Gaithersburg, MD.
Vitamin B
12
–AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Methods 952.20
and 960.46, AOAC International, Gaithersburg, MD.
Vitamin C –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Method 967.22,
AOAC International, Gaithersburg, MD.
Vitamin D –Covance Laboratories Internal Method.
Vitamin E –Cort WM, Vincente TS, Waysek EH,
Williams BD. 1983. Vitamin E content of feedstuffs
determined by high-performance liquid chromatography
fluorescence. J Agr Food Chem 31:1330-1333.
Vitamin K –AOAC. 2005. Official Methods of
Analysis of AOAC International, 18th Ed. Methods 992.27,
and 999.15, AOAC International, Gaithersburg, MD.
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Complete Nutrient Content of Four Species of Feeder Insects 11
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