Diversity of Floricultural Insects and their impact on the Productivity of Cucurbita Maxima Dusch (Cucurbitaceae) in the Sudano-Sahelian Zone of Cameroon

Abstract

Purpose: This study aims to assess the biodiversity of Cucurbita maxima pollinators with a view to optimising the expected results, in a context of efficient and sustainable agriculture in Cameroon. Methodology: In Vogzom (North), and in Torok (Far North) in 2022, Cucurbita maxima flowers (Cucurbitaceae) were observed in order to evaluate agronomic parameters, identify the floricultural entomofauna and the pollinating activity of Apidae. For the characterization of the floricultural entomofauna in Vogzom and Torok, five treatments of 30 female flowers each were established according to whether they were protected from visits by Apis mellifera (T0) or benefited from one visit (T2), two (T3), three visits (T4) each or were free (T1). A recognition code was assigned to each visiting species of Cucurbita maxima flowers and a few individuals of each species were captured and retained for later identification. The data collected was codified and encoded in the Excel spreadsheet of the Microsoft Office 2019 program. The normality test of the different variables was done by the Shapiro-Wilk test at the 5% significance level. The Tukey test was used for the comparison of means when the p-value was ˃ 5% and otherwise, the nonparametric Kruskal-Wallis test was used. Finding: The floricultural entomofauna associated with pumpkin consists of five species in Vogzom and fourteen species in Torok. Apidae (82.06%) were in the majority; represented by Apis mellifera (82.06%) in Vogzom. Similarly in Torok, Apidae (77.55%) were in the majority, represented by Apis mellifera with a relative abundance of 40.5%. The daily activity of the Apidae was effective between 6 a.m. and 1 p.m. with a morning peak of activity (6 a.m. to 7 a.m.) in both sites. Floral visits to collect nectar (74%) were more important than those devoted to pollen (26%) in A. mellifera. In Vogzom as well as in Torok. The fruiting and mature fruit rates as well as their average mass vary according to the number of successful insect visits by the female flowers. Contributions to theory, policy and practice: Overall, the fruit and seed production of Cucurbita maxima is closely dependent on the pollinating activity of the Apidae; without it, no fruit or seed is formed, as the pumpkin is neither parthenocarpic nor apomictic. Obtaining optimal pumpkin yields is conditioned by the conservation and protection of pollinator biodiversity.

Full text

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Diversity of Floricultural Insects and their impact on the
Productivity of Cucurbita Maxima Dusch (Cucurbitaceae) in the
Sudano-Sahelian Zone of Cameroon

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Diversity of Floricultural Insects and their impact on the Productivity of
Cucurbita Maxima Dusch (Cucurbitaceae) in the Sudano-Sahelian Zone of
Cameroon
Hebri Sanda1*, Angoni Hyacinthe1, Zéphirin Oumarou Haman3, Abdouraman4, Joseph
Messi Effa1, Menyene Etoundi Laurent Florent1, Tchobsala2.
1Department of Plant Biology and Physiology, Laboratory of Botany and Ecology, Faculties
of Science, University of Yaoundé, Cameroon
2 Department of Biological Sciences, Laboratory of Botany, University of Maroua, Cameroon
3Department of Biological Sciences, Faculties of Science, University of Bamenda, Cameroon
4 Laboratory of Biodiversity and Sustainable Development, Faculty of Sciences, University of
Cameroon.
https://orcid.org/0009-0007-1511-961X
Accepted: 5th Jan 2025 Received in Revised Form: 20th Jan 2025 Published: 11th Feb 2025
Abstract
Purpose: This study aims to assess the biodiversity of Cucurbita maxima pollinators with a view to
optimising the expected results, in a context of efficient and sustainable agriculture in Cameroon.
Methodology: In Vogzom (North), and in Torok (Far North) in 2022, Cucurbita maxima flowers
(Cucurbitaceae) were observed in order to evaluate agronomic parameters, identify the floricultural
entomofauna and the pollinating activity of Apidae. For the characterization of the floricultural
entomofauna in Vogzom and Torok, five treatments of 30 female flowers each were established
according to whether they were protected from visits by Apis mellifera (T0) or benefited from one visit
(T2), two (T3), three visits (T4) each or were free (T1). A recognition code was assigned to each visiting
species of Cucurbita maxima flowers and a few individuals of each species were captured and retained
for later identification. The data collected was codified and encoded in the Excel spreadsheet of the
Microsoft Office 2019 program. The normality test of the different variables was done by the Shapiro-
Wilk test at the 5% significance level. The Tukey test was used for the comparison of means when the
p-value was ˃ 5% and otherwise, the nonparametric Kruskal-Wallis test was used.
Finding: The floricultural entomofauna associated with pumpkin consists of five species in Vogzom
and fourteen species in Torok. Apidae (82.06%) were in the majority; represented by Apis mellifera
(82.06%) in Vogzom. Similarly in Torok, Apidae (77.55%) were in the majority, represented by Apis
mellifera with a relative abundance of 40.5%. The daily activity of the Apidae was effective between 6
a.m. and 1 p.m. with a morning peak of activity (6 a.m. to 7 a.m.) in both sites. Floral visits to collect
nectar (74%) were more important than those devoted to pollen (26%) in A. mellifera. In Vogzom as
well as in Torok. The fruiting and mature fruit rates as well as their average mass vary according to the
number of successful insect visits by the female flowers.
Contributions to theory, policy and practice: Overall, the fruit and seed production of Cucurbita
maxima is closely dependent on the pollinating activity of the Apidae; without it, no fruit or seed is
formed, as the pumpkin is neither parthenocarpic nor apomictic. Obtaining optimal pumpkin yields is
conditioned by the conservation and protection of pollinator biodiversity.
Keywords: Cucurbita Maxima, Productivity, Pollination, Food Security, Sudano-Sahelian

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1. Introduction
Many insects visit the flowers, which are a source of sweet and protein food for them (Guerriat,
1996). They are responsible for the pollination of more than 80% of cultivated plants (Klein et
al., 2007) and represent the most numerous and efficient pollinators (Philippe, 1991). The floral
activity of pollinating insects promotes the reproduction of angiosperms and leads to an increase
in the quantity and quality of the yields of plant species (Pesson & Louveaux, 1984 and Klein
et al. 2007). Crop pollinating insects are in the process of accelerated dieback throughout the
world (Haubruge et al., 2006). However, they are an essential link in the food chain, for the
survival of several wild and cultivated plant species. According to the FAO (2005), each state
must develop a policy for the protection and conservation of pollinating insects; This requires
a good knowledge of plant-pollinator networks. Thus, in several countries, pollinating insects
of several plant species are known and their activity meticulously exploited (Jacob-Remacle,
1989). It is well known in the literature that the activity of floricultural entomofauna associated
with spontaneous or cultivated plant species usually leads to increased fruit and/or grain yields
via pollination (Jacob-Remacle, 1989).
Given its economic importance, the preciousness of its fruits in the human diet and considering
the need to maintain and increase its fruit and seed production, we studied the entomophilous
pollination of pumpkin or Cucurbita maxima. The general objective of this study is to contribute
to the knowledge of the relationships between Cucurbita maxima and its antophilic insects in
order to optimize the expected results, in a context of efficient and sustainable agriculture in
Cameroon. Specifically, to evaluate the diversity of flowering insects of Cucurbita maxima and
the substances collected in order to determine the pollinating potential and their impact on the
fruit and seed yield of this crop.
2. Literature Review:
In Cameroon, studies on the pollination of Cucurbitaceae have only focused on pistachio or
Cucumeropsis mannii (Azo'o & Messi, 2012), watermelon or Citrullus lanatus and wild
cucumber Cucumis sativus (Azo'o et al., 2014 and 2017). Despite this work, additional
information is not yet exhaustive on the knowledge of the relationships between several plant
species growing in Cameroon and their pollinating insects (Tchuenguem, 2010b). For the
moment, no studies have been carried out on the pollination of pumpkin in this country.
3. Materials and Methodology
3.1. Sites, study stations and biological materials
Investigations took place in Torok, in the district of Guidiguis, Far North region, and in
Vogzom, in the district of Touboro, in the North region of Cameroon in 2022 (fig. 1). The
choice of these observation sites is justified by the large number of Cucurbita maxima
producers, the existence of farmers' fields of other crops and the guarantee of safety of the
experimental plots and the observer. The plant material consisted of pumpkin seeds bought at
the local markets. All the insects present in the investigation sites constitute animal material.

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Figure 1: Location map of the Torok and Vogzom study sites
3.1.1. Experimental Devices
The study of the activity of antophilic insects on C. maxima was carried out from a randomized
experimental design and took place during the entire flowering period during the production
season of the year 2022. 30 plants were chosen on a random basis and divided into two blocks.
The female flowers from these two blocks are labelled and two treatments are made up
depending on whether or not they are isolated from the foraging activity of the flowering
insects: treatment A and treatment B each constituted 30 female flowers. Overall, the marking
and isolation of female flowers in Batch B was carried out the day before they opened. The next
day after they were isolated, the mosquito nets were removed, allowing the evolution of the
potential fruit formed to maturity to be followed.
3.2. Method
3.2.1. Diversity of the flower-dwelling entomofauna of Cucurbita maxima
3.2.1.1. Collection of data on the flowery entomofauna of Cucurbita maxima.
Observations are made every day on the flowers of the plants left in free pollination between 6
a.m. and 1 p.m. (periods corresponding to the beginning and end of insect visits), during the
flowering period of the plant species under study. The activity of the antophilic insects was
recorded during four daily time slots: 6 - 7 a.m., 8 - 9 a.m., 10 -11 a.m. and 12 - 1 p.m. At each
time slot of observation, the number of visiting insects was carried out, the number of visiting
insects was passed in front of each labelled plant in block (A) and counted on the open flowers.
The cumulative results of the different counts are expressed by the number of visits
(Tchuenguem et al., 2004). Based on the data on the floricultural entomofauna, some ecological
parameters (Shannon, Jacrd and Piélou equitability indices) were evaluated in order to assess
the species richness of the insects in the two study sites.

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3.2.1.2. Variations in insect flower visits according to the rate of flowering of Cucurbita
maxima flowers.
Each day, the cumulative visits of the antophilic insects that are listed as active on the flowers
of the plant species by time slot are listed. These visits are brought closer together at the daily
rate of the blossoming of the unisexual flowers, the count of which is derived from the previous
protocol.
1. Average duration of floral visit and floral preferences and influence of abiotic
factors on forager activity.
This is the time it takes for the insect to collect a product (pollen and/or nectar) from a flower
(Jacob-Remacle, 1989). The duration of a visit corresponds to the value read on the stopwatch
when the insect left the flower (Tchuenguem et al., 2004).
Floral preferences indicate the attractiveness of floral products (nectar and pollen) on the
foraging activity of the anthophile insects listed (Messi & Tchuemguem, 1994).
The temperature and humidity of the study station were recorded twice per daily observation
time slot using a portable thermo-hygrometer and their average values were calculated (Azo'o
et al., 2021).
3.2.2. Method for evaluating the performance of Cucurbita maxima
3.2.2.1. Pollination efficiency studies
Treatment C (T2) which consisted of 30 female flowers each of which had benefited from a
single visit from a major insect. Treatments D (T3) which consisted of 30 female flowers that
each benefited from 2 simultaneous visits of major insects. Treatment E (T4) consisted of 30
female flowers, each of which benefited from 3 simultaneous visits of major insects.
Figure 2: Free female flower (Hebri,2022) Figure 3: Isolated female flower (Hebri,2022)
3.3. Data analysis and Processing
3.3.1. Analysis and processing of data on the impact of pollinators on the yield of Cucurbita
maxima.
3.3.1.1. Forager density
The density of foragers (A) is the largest number of individuals simultaneously active on a
given number of flowers (Jacob-Remacle 1989). It is expressed by the ratio between the number

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of foragers counted (Ax) and the number of flowers in bloom (Fx) at time x. For practical
reasons, this ratio is multiplied by 100 or 1000, which gives the number of individuals observed
for 100 or 1000 flowers present at a given time (Pierre et al., 1997). The corresponding formula
is therefore A = [(Ax/Fx) x 100 or 1000] (Tchuenguem et al., 2004).
3.3.1.2. Fruiting rate due to pollinators
In the 6 treatments constituted, the fruiting rate [(number of fruits formed/number of female
flowers studied) x 100] is calculated. The fruiting rate (%Tfr) attributable to antophilic insects
is estimated by the formula (%Tfr) = {[(TA – TB)/TA] x 100} where TA and TB are respectively
the fruiting rates in treatment A (female flowers without protection) and in treatment B (female
flowers protected from insect floral activity) (Tchuenguem et al., 2004).
3.3.1.3. Pollination rate due to pollinating insects
The mature fruits of Cucurbita maxima are weighed by a kitchen scale; opened with a machete
and the number of mature seeds (Gm) and immature seeds (Gi) are counted. The nature of the
seeds allows us to estimate the pollination rate (P): P (%) = {[(Gm/Gm + Gi)] /100} according
to Gingrass et al. (1999). In addition, a linear relationship can be established between the mass
of each fruit and the number of mature seeds counted to assess the relationship between these
two parameters Nerson, (2002).
3.3.1.4. Rates of mature seeds attributable to pollinators
As with the calculation of the fruiting rate due to pollinating insects, the same reasoning is
applied to the calculation of the percentage of mature seeds per fruit due to the floral activity
of antophilic insects (Tchuenguem et al., 2004).
4. Results
4.1. Biological diversity of insects on Cucurbita maxima flowers.
At the order level, the flowering insects of the pumpkin in Vogzom were divided into three
main orders. The order Hymenoptera is predominant with 85.58% of the total number of visits,
the order of Coleoptera with 9.13% of the relative abundance and the order of Diptera with only
5.29% of the number of visits. The flowering insects of the pumpkin have been grouped into 4
families; they are classified as follows in descending order of their relative abundance: the
family Apidae (82.06%), the family Leaf beetles (9.13%), the family Drosophila (5.29%) and
the family Haicelidae (3.52%). Five species of antophilic insects have been identified active
on the flowers of Cucurbita maxima. The honey bee A. mellifera is prominent with a relative
abundance of visits of 82.06%; this bee is the only representative of the family Apidae. The
other species are in descending order of their relative abundance: Drosophila melanogaster
(5.29%), Monolepta intermedia (4.93%), Monolepta bioculata (4.20) and Lasioglossum sp.
(3,52%). Overall, the flower-dwelling entomofauna of Cucurbita maxima in Vogzom
(Touboro, Cameroon) is poorly diversified and largely dominated by the activity of A. mellifera.
On the other hand, in Torok, the floricultural entomofauna of Cucurbita maxima is divided into
three orders of unequal importance due to the variation in their relative abundance. The order

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of hymenoptera is dominating with 82.3% of the total number of visits, followed by lepidoptera
and diptera with a relative abundance of 11.1% and 3.4% respectively. As far as the family is
concerned, the floricultural insects are divided into 9 families and dominated by the apidae,
with a relative abundance of 77.55% of the total number of visits, followed respectively by the
halictidae (4.1%), meachilidae (3.9%), nymphalidae (3.6%), pieridae (2.7%), acraeidae (2.5%),
papilionidae (2.3%), syrphilidae (2.00%) and finally drosophilidae (1.4%). Fourteen species of
antophilic insects have been recorded active on the flowers of Cucurbita maxima. Apis mellifera
is dominant with a relative abundance of 40.5%, while Trinchostoma sjostedti is the lowest
(0.9%) of the total number of visits. Overall, the flower-dwelling entomofauna of Cucurbita
maxima in Torok (Far North) is diverse and dominated by the activity of Apis mellifera. The
results of the biological diversity of the flowering entomofauna associated with Cucurbita
maxima, Vogzom (North) and Torok (Extreme-North) are reported in Table I below.
4.1.1. Index of diversity of entomofauna between the two sites
The Shannon diversity index calculated at the two sites was respectively H' = 2.70p at Torok
(Far North) and H' = 1.03 at Vogzom (North). Species diversity is low at Vogzom (North) H' <
3 compared to Torok (Far North) which is average (2 < H' < 4). The site of Torok (Far North)
is thus rich in flowering species of pumpkin more than the site of Vogzom (fig. 40.).
The calculated values of the Pielou equitability, linked to the Shannon index, confirm the
fluctuations between these values of the diversity index. The equitability values show an almost
equal variation in the two sites.
In addition, the Simpson index proves that the probability of two individuals taken at random
being different species is low. The low values of the indices in intercropping (0.2) as well as in
non-associated crops (0.15) and 0.28 in shrub savannahs show that they are poor in biodiversity.
This low diversity is the consequence of human activities developed in the fields, in particular
with the abusive use of chemical inputs.
4.2 Insect activity at the flower level Cucurbita maxima
4.1.2. Rhythm of visits according to the rhythm of blooming of the flowers of Cucurbita
maxima
Overall, the number of insect visits varies depending on the number of blooming flowers. In
the Far North, as in the North, the bell-shaped curve shows that the number of flowers in bloom
increases and reaches a peak and then decreases until wilting. It is important to note that the
higher the number of flowers, the higher the number of insect visits. It also emerges from these
figures that there is a positive and significant correlation between the number of flowers in
bloom and the abundance of visitors to Torok in the Far North (r = 0.93; ddl = 14; P < 0.001)
as well as in Vogzom in the North (r = 0.92; ddl = 4; P > 0.01). These correlations highlight the
good attractiveness of the nectar of the flowers of this Cucurbitaceae to foragers.
Figure 4 illustrates the relationship between the number of Cucurbita maxima flowers blooming
per day and the corresponding number of insect flower visits.

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Table I. Number and percentage of visits of the different insects recorded at the level of
Cucurbita maxima flowers in 2022 (Cameroon).
Floricultural insects
Torok (Far North)
Vogzom(North)
Order
Family
Genus and Species
n1
f1 (%)
n2
f2 (%)
Hymenoptera
Apidae
Apis mellifera
528
40,5
1349
82,06
Xylocopa inconstans
261
19,7
Xylocopa pubescens
195
14,7
Xylocopa olivacea
42
3,2
Total Apidae
4
1026
77,55
1349
82,05
Halictidae
Lipotriches collaris
42
3,2
Lasioglossum sp.
58
3,52
Trinchostoma sjostedti
12
0,9
Total Halictidae
3
54
4,1
Megachilidae
Megachile aurifera
51
3,9
Total Megachilidae
1
51
3,9
58
3,52
Total Hymenoptera
4
8
1089
82,3
1407
85,58
Coleoptera
Chrysomelidae
Monolepta intermedia
81
4,93
Monolepta bioculata
69
4,2
Total Chrysomelidae
2
150
9,13
Total Coleoptera
1
2
150
9,13
Diptera
Syrphidae
Phytomia sp.
15
1,1
1 sp.
12
0,9
Total Syrphidae
2
27
2,00
Drosophilidae
Drosophila melanogaster
18
1,4
87
5,29
Total Drosophilidae
1
18
1,4
87
5,29
Total Diptera
2
3
45
3,40
87
5,29
Lepidoptera
Nymphalidea
Hypolimnas misippus
48
3,6
Total Nymphalidea
1
48
3,6
Papilionidea
Papilio demodecus
30
2,3
Total Papilionidea
1
30
2,3
Pieridae
Eurema exima
21
1,6
Catopsilia florella
15
1,1
Total Pieridae
2
36
2,7
Acraeidae
Acraea acerata
33
2,5
Total Acraeidae
1
33
2,5
Total Lepidoptera
4
5
147
11,1
Total
14
1323
100,0
1644
100
p = (n/1644) x 100 = Percentage of visits; n = number of visit

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Figure 4: Variation in the number of visits according to the number of flowers in bloom
4.1.2.1.Absolute abundance of visiting insects
The greatest number of individuals simultaneously active on a flower was 2 in A. mellifera and
one in all other insects at the two sites, respectively. The average abundance per 1000 flowers
varied from 31 in A. mellifera to 5 in Xylocopa olivacea in Torok (Far North) and from 958 in
A. mellifera to 182 in Lasioglossum sp in Vogzom in the north. The optimal value of the density
of foraging insects corresponded to the month of peak flowering of the plant species studied,
which is the month of August in the Sudano-Sahelian zone of Cameroon. Tables II and III
below present the results relating to the abundance of visits of two Apidae on the flowers of
Cucurbita maxima in Torok (Far North) and Vogzom (North).
Table II. Abundance of foragers of some insects per flower, Cucurbita maxima, in Torok
(Far North) and Vogzom (North).
Parameters studied
Insects
Torok (Far North)
Vogzom (North)
n
m ± s
mini
maxi
N
m ± s
mini
maxi
Apis mellifera
65
2.03 ± 0.79
1
4
67
2.26 ± 1.45
1
4
Xylocopa inconstans
36
1.03 ± 0.18
1
2
Xylocopa olivacea
48
1.00 ± 0.00
1
1
Lasioglossum sp.
50
1.04 ± 0.19
1
2
n : number of timed visits; m : mean; S : standard deviation; mini : minimum; Max: maximum.
Table III. Average abundance of foragers of some insects per 1000 flowers in Torok (Far
North) and Vogzom (North).
Parameters studied
Insects
Torok (Far North)
Vogzom (North)
n
m ± s
mini
maxi
N
m ± s
mini
maxi
Apis mellifera
59
31.42 ± 16.11
64
625
67
958.54 ± 676.92
111
2667
Xylocopa inconstans
30
6 ± 1.30
1
12
Xylocopa olivacea
15
5 ± 10
1
11
Lasioglossum sp.
50
182.22 ± 89.11
111
444
Legend: n = sample; m = mean; s = standard deviation; mini = minimum; max = maximum
0
50
100
150
200
250
300
350
400
450
0
10
20
30
40
50
60
70
10 12 14 16 18 20 22 24 26 28 30 1 3 5 7
Nombre de visites d'insectes
Nombre de fleurs épanouies
Jour d'observation (Août - septembre 2022)
Nombre de fleurs
épanouies
Nombre de visites
d'insectes

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Figure 5: Cucurbita maxima flower foraged by several workers (Hebri, 2022)
4.1.2.2.Average duration of visits of Apidae per flower
The duration of visits was recorded in Apidae for both nectar and pollen collection visits.
Pollen was collected from male flowers and nectar from both sexes, male and female flowers.
The average duration of a visit per Cucurbita maxima flower varies according to the floral
product harvested and for each floral product, depending on the species of insect and depending
on the site.
On female flowers in the Torok site (Far North) the average duration of a visit varies
from 6.15 (n = 134; s = 2.42) seconds in Xylocopa inconstants at 4.24 (n = 379; s = 2.42)
seconds in Apis mellifera. Comparison of the mean length of visits between the two insect
species on female flowers indicates a significant difference (t = 11.93; ddl = 208; P < 0.05). In
Vogzom in the North, on female flowers, the average duration of a visit varies from 315.06 (n
= 19; s = 146.30) seconds in Lasioglossum sp. 13.35 (n = 698; s = 20.56) seconds in Apis
mellifera. Comparison of the mean length of visits between the two bee species on female
flowers indicates a significant difference (t = 9.31; ddl = 145; P < 0.05).
On male flowers in the Torok site (Far North), the average duration of a visit varies
from 5.28 (n = 34; s = 3.02) second in Xylocopa olivaceae at 3.80 (n = 1491; s = 1.86) seconds
in A. Mellifera; Comparison of the mean length of visits between the two bee species on male
flowers indicates a significant difference (t = 9.31; DDL = 145; P < 0.05). The same pattern in
Vogzom (North) the average duration of a visit varies from 12.57 (n = 36; s = 3.02) second in
Lasioglossum sp. and 4.11 (n = 651; s = 1.83) seconds in A. Mellifera; The comparison of the
average length of visits between the two insect species indicates a significant difference (t =
9.31; DDL = 145; P < 0.05). Overall, the average values of the Apidae visit time are higher for
nectar collection than for pollen. The values for the average length of visits for nectar or pollen
collection are reported in Tables IV and V below.

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Table IV. Average duration of a visit of the Apoidea species on the female flowers of
Cucurbita maxima in Torok (Far North) and Vogzom (North).
Study sites
Insects
Torok (Far North)
Vogzom (North)
N
m ± s
Mini
maxi
N
m ± s
Mini
maxi
Apis mellifera
379
4.24 ± 1.29
1
7
698
13.35 ± 20.56
1
125
Xylocopa inconstans
134
6.15 ± 2.42
1
8
Xylocopa olivacea
38
2.11 ± 1.21
1
6
Lasioglossum sp.
19
315.06 ± 146.30
5
2340
Table V Average duration of visit of Apidae on male flowers of Cucurbita maxima in
Torok (Far North) and Vogzom (North).
Study
sites
Insects
Torok (Far North)
Vogzom (North)
N
m ± s
Mini
maxi
N
m ± s
mini
maxi
Apis mellifera
1491
3.80 ± 1.86
1
10
651
4.11 ± 1.83
1
5
Xylocopa inconstans
34
5.28 ± 3.41
1
8
Xylocopa olivacea
51
2.04 ± 0.43
1
5
Lasioglossum sp.
36
12.57 ± 3.02
1
54
4.1.2.3.Floral products harvested
Out of 528 and 1015 visits Apis mellifera studied in Torok (Far North) and Vogzom
(North of the North) respectively), 416 (78.78%) and 681 (67.09%) were devoted primarily to
nectar collection (Figure 7), 91 (17.23%) and 305 (30.04%) to simultaneous pollen and nectar
collection, 21 (3.97%) and 29 (2.85%) to exclusive pollen collection (Figure 8). In Torok, the
261 and 195 visits of Xylocopa inconstans and Xylocopa olivacea studied were devoted
exclusively to the exclusive collection of nectar. 32 (55.17%) and 26 (44.82%) to the collection
of nectar and pollen, out of 58 visits to Lasioglossum sp. at Vogzom.
With the exception of Apis mellifera which selectively and alternately collects pollen and
nectar from the male flowers of Cucurbita maxima during the same visit, the results obtained
illustrate that: the honey bee is fonder of nectar than pollen on the flowers of C. maxima. Data
on the proportion of removals of the two floral products by Apidae are given in Table VI below.
Table VI. Floral preferences of Apidae on Cucurbita maxima
Floral Products
Insects observed
NVE
Nectar
Nectar and Pollen
Pollen
NVN
%
NVPN
%
NVP
%
Apis mellifera
528
416
78,78
91
17,23
21
3,97
Xylocopa inconstans
261
261
100,00
Xylocopa olivacea
195
195
100,00
Torok (Far North)
Apis mellifera
1349
681
67,09
305
30,04
29
2,85
Lasioglossum sp.
58
32
55,17
26
44,82
Vogzom (North)

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Legend: NVE = Number of visits studied; NVN = Number of visits devoted to nectar
harvesting; NVPN = Number of visits devoted to the collection of nectar and pollen; NVP =
Number of visits dedicated to pollen collection
Figure 6: Apis mellifera nectarivore Figure 7: Apis mellifera pollinivore
4.1.3. Influence of some abiotic factors on the antophilic activity of foragers
Flower visits by flowering insects are more important in the morning, when the
temperature is low (19.9°C) and the relative humidity high (84.81%). However, insect flower
visits gradually decrease with increasing temperature and decreasing relative humidity. Overall,
insect flower visits are strongly correlated with variations in air temperature and relative
humidity. The linear regression is negative and significant between temperature and number of
visits (y = -0.0147x + 30.95) with a high coefficient of determination (R2 = 0.9734; ddl = 1, 3;
P < 0.05) (Figure 9). The high temperature is detrimental to the insects foraging activity on
pumpkin flowers.
Figure 8: Linear regression equation between the number of visits and temperature
y = -0,0147x + 30,95
R² = 0,97
0
5
10
15
20
25
30
0 200 400 600 800
Température (°C)
Nombre de visites

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4.2.Yield evaluation due to pollinating insects of Cucurbita maxima
4.2.1. Impact of insects on pollination C. maxima
When collecting pollen and/or nectar from a C. maxima flower, insects were frequently
found in contact with the anthers and stigma. Some insects carried the pollen of the plant species
studied from flower to flower (with the help of mouthparts and fur) on one or more pistillate
flowers borne by the same plant. They could therefore intervene in geitonogamimy (transport
of pollen grains from a male flower to a female flower carried by the same melon plant) or in
xenogamy (transport of pollen grains from a male flower from plant A to a female flower carried
by another melon plant B). As a result, these insects were actively involved in the cross-
pollination of Cucurbita maxima.
For each of the two sites, in apidea (Apis mellifera, Xylocopa inconstans, Xylocopa
olivacea); the frequency of contact between the stigma and the anthers during foraging was
100%. While in Lasioglossum sp., the frequency of visits with insect-stigma contact was
90.47% and 88.88% with anthers. Table VII shows the frequency of contact between insects
and the stigma of pumpkin flowers, for which the duration of visits per flower was recorded.
Table VII. Number and frequency of contacts between insects, anthers and stigma
during floral visits of Cucurbita maxima in Torok (Far North) and Vogzom (North).
Insects
Number of
visits studied
Visits with
stigmatic contact
Number of
visits studied
Visits with anther
contact
n
N
(%)
n
Number
(%)
Apis mellifera
640
640
100,00
1491
1491
100,00
Xylocopa
inconstans
261
261
100,00
34
34
100,00
Xylocopa olivacea
195
195
100,00
51
51
100,00
Torok (Far North)
Apis mellifera
1349
1349
100,00
651
651
100,00
Lasioglossum sp.
84
76
90,47
36
32
88,88
Vogzom (North)
4.2.2. Fruit and seed yields of Cucurbita maxima
C. maxima flowers that do not benefit from insect floral visits (Treatment B) abort and fall off.
Only the flowers that benefited from insect floral visits (Treatment A and C) produced fruits
and seeds as future seeds. The floral activity of insects on the flowers of C. maxima conditions
the fruit and seed production of this plant species. In the Torok site (Far North), the fruiting rate
was 76.67% in treatment A, 0% in treatment B and 26.66% in treatment C. The overall
comparison indicates a significant difference between treatments A, B and C (x2 = 40.25; ddl =
2; P < 0.05) and between treatments A and C (x2 = 15.02; ddl = 1; P < 0.05). And in Vogzom
(North), the fruiting rate is 93.33% in treatment A, 0% in Traitemen B and 43.33% in treatment

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C. The overall comparison indicates a significant difference between treatments A, B and C (x2
= 52.77; ddl = 2; P < 0.05) and between treatments A and C (x2 = 17.33; ddl = 1; P < 0.05)
The mean number of mature seeds per fruit was 255.31 ± 51.02 and 252.33 ± 38.02 in Treatment
A in Torok (Far North) and Vogzom (North) respectively and zero in Treatment B at both sites
since there was no fruit formation in these two treatments. From Tables VIII and IX below, the
pollination rate is deduced through the ratio between the total number of mature seeds (NGM)
obtained to the total number of sheaths (NTG) which reflects the total number of ovules
obtained. This rate is [(2925/3028) x 100] = 96.59% [(6521/6638) x 100] = 98.23%.
Respectively in Torok and Vogzom. This high rate reflects the fact that good pollination leads
to good fertilization and an increase in seed and fruit yield in Cucurbita maxima. Bees are
therefore responsible for improving fruit and seed yields in pumpkins.
The fruiting rate and number of mature seeds were zero in the T0 control treatment in which
the female flowers were exempted from insect flower visits. This rate is 93.33% and 98.23%
respectively in the T1 treatment whose flowers are kept in open pollination. The fruiting rate
attributable to Apidae is {[(93.33 – 0.00)/93.33] x 100} = 100%. Similarly, the percentage of
mature seeds attributable to honey bee pollinator activity is {[(93.33 – 0.00)/93.33] x 100} =
100%. The mean mass of mature fruit in the two sites was 4.26 kg. Overall, Apidae in general
and the honey bee in particular contribute to the maintenance of fruit and seed production of
Cucurbita maxima. The fruit and seed yield of Cucurbita maxima in Torok and Vogzom
according to the different traitements.et recorded in tables VIII and IX below.
Table VIII. Fruit and pumpkin seed yields in Torok (Far North).
Parameters studied
Treatment A
Treatment
B
Treatment C
Number of flowers studied
30
30
30
Number of fruits formed
23
0
8
Percentage of fruit formed (%)
76,67
0
26,66
Number of mature fruits obtained
12
0
0
Percentage of fruit that has reached maturity (%)
52,17
0
0
Total number of seeds obtained
3028
0
0
Number of mature seeds obtained
2925
0
0
Percentage of mature seeds obtained (%)
96,60
0
0
Number of immature seeds obtained
103
0
0
Percentage of immature seeds obtained (%)
3,40
0
0
Average number of mature seeds per fruit
252 ± 38
0
0
Abortion rate (%)
48
100
100

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Table IX. Fruit and seed yields of Cucurbita maxima in Vogzom (North).
Parameters studied
Treatment A
Treatment
B
Treatment C
Number of flowers studied
30
30
30
Number of fruits formed
28
0
13
Percentage of fruit formed (%)
93,33
0
43,33
Number of mature fruits obtained
26
0
2 (Fbtvi)
Percentage of fruit that has reached maturity (%)
92,85
0
15,38
Total number of seeds obtained
6638
0
84
Number of mature seeds obtained
6521
0
30
Percentage of mature seeds obtained (%)
98,23
0
35,71
Number of immature seeds obtained
117
0
54
Percentage of immature seeds obtained (%)
1,76
0
64,28
Average number of mature seeds per fruit
255 ± 51
0
15
Abortion rate (%)
7,15
100
85
Legend : (Fbtvi) : female flowers, each of which benefited from 3 simultaneous visits of insects.
4.2.2.1.Linear relationship between fruit mass and number of mature seeds
Figure 11 below illustrates the linear regression equation between fruit mass and the
number of mature seeds contained in each fruit. It can be seen from this figure that there is a
positive and significant regression equation between these two parameters (y = 102.57x +
36.418) with a coefficient of determination R2 = 0.89 (ddl = 1.19; p ˂ 0.05). This coefficient of
determination indicates that 89% of the variation in the number of mature seeds influences the
mass of the fruits obtained. Overall, the larger the fruit, the higher the number of mature seeds
it usually contains.
Figure 9 : Linear relationship between fruit mass and number of mature seeds
5. Discussion
The identification of pollinating insects on Cucurbita maxima in the Sudano-Sahelian zone of
Cameroon has shown that the floricultural entomofauna associated with this crop is low in
Vogzom (North) and diversified in Torok. It is represented by only 3 orders, 4 families and 5
y = 102,57x + 36,418
R² = 0,88
0
100
200
300
400
500
600
0 1 2 3 4 5
Nombre de graines
matures
Masse des fruits en Kg

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species in Vogzom, while in Torok it is made up of 3 orders but 14 families and 29 species. The
work of other authors on other cultivated plant species of Cucurbitaceae or not has recorded a
relatively high number of species of flowering insects. Azo'o (2014) recorded 38 insect species
on the flowers of Citrullus lanatus, 35 on Cucumeropsis mannii and 14 on Abelmoschus
esculentus in Yaoundé. Overall, the floricultural entomofauna varies from one plant species to
another, with variations in the number of species identified and the different species obtained.
The results of this work also indicate the prominence of Apidae in the floricultural entomofauna
of pumpkin with two species, namely, Apis mellifera and Lasioglossum sp in Vogzom and Apis
mellifera, Xylocopa inconstans, Xylocopa pubescens, Xylocopa olivacea in Torok. Of these
insect species at both sites, A. mellifera comes out on top with a relative abundance of 82.06%
and 40.5% respectively in Vogzom and Torok. Honeybees are known as the main flowering
and pollinating insects of several other Cucurbitaceae species: Cucurbita moschata Canto-
Aguilar & Parra-Tabla., (2000), Cucumis sativus (Gingrass et al., 1999; Calin et al., 2008).
The activity of Apidae in general and A. mellifera in particular is predominant in the morning
from dawn and ends at midday (before 1 p.m.). It is known in the literature that pumpkin
flowers, like other Cucurbit species such as watermelon, have an ephemeral lifespan (Philippe,
1991; Petersen et al., 2013 and Bomfim et al., 2016); thus, they produce a lot of nectar in the
morning from the anthesis. In addition, the peak of bee activity on the flowers of plant species
is generally correlated with the greater availability of floral resources such as nectar and pollen,
which explains the principle of optimal foraging that characterizes social bees (Pierre, 1997).
Apis mellifera appeared mainly as a nectarivore on the flowers of Cucurbita maxima in the
observation site at Torok and Vogzom. The results of this study indicate that 78.78% and
67.09% of the visits were devoted to the collection of nectar in Torok and Vogzom respectively.
Similar results have been obtained on bee foraging activity on other Cucurbit species such as
the watermelon Citrullus lanatus (Cordova, 1990 and Knapp et al., 2018) and Cucumeropsis
mannii (Azo'o & Messi, 2012).
The results of this study show that there is a positive and significant correlation between the
daily rhythm of flower bloom and the rhythm of floral visits of insects in general and Apidae
in particular. This correlation highlights a second aspect that illustrates the principle of optimal
supply or forage that characterizes the Apidae, particularly A. mellifera (Pierre, 1997).
According to Faegri & Pijl (1979), the availability of floral resources plays an important role in
bee foraging and pollination. These data underlie Fretwell & Lucas' (1970) theory of the ideal
free distribution, which states that pollinator abundance follows the spatial distribution of
flower densities in the field. Similar results have been obtained by several authors on several
plant species, such as (Tchuenguem et al., 2009a) on Helianthus annus and (Djonwangwé et
al., 2011) on Ximenia americana. This work also highlights the high quantity of male flowers
compared to female flowers in the site of Torok and Vogzom. This predominance of the number
of male flowers over the number of female flowers suggests the wide availability of pollen,
which is advantageous for the pollination of female flowers.

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The high abundances of A. mellifera on 1000 flowers highlight the good attractiveness of the
nectar and the large landing surface of Cucurbita maxima flowers. Indeed, it is known that in
A. mellifera, during foraging, workers use the pheromone to mark interesting food sources, with
a view to directing other foragers to them (Jacob-Remacle, 1990). In addition, the experimental
site in Vogzom was located near an apiary, hence the large deployment of workers on Cucurbita
maxima flowers.
During their visits to the staminate flowers of Cucurbita maxima, honeybees in general came
into contact with the anthers and passively collected pollen with their thick fur. Passing over
the female flowers, the foragers came into contact with the stigmas and induced pollination of
the female flowers visited. Vaissière et al. (1998) report that in entomophilous plants from
which Cucurbitaceae originate (Klein et al. 2007), pollination requires the transfer of pollen
through the bee seed coat.
Cucurbita maxima , like all other Cucurbitaceae, is a self-compatible and inter-compatible plant
species and the pollen grains of this crop are not anemophilic, i.e. cannot be carried by the wind
(Cordova, 1990). Only bees A. mellifera were found to be suitable for interfloral transport of its
pollen, which favoured fertilisation in this plant species in both Torok and Vogzom. The
significant activity of honey bees from the blossoming of the flowers coincides with the period
of maturity of the stamens and receptivity of the stigmata of Cucurbitaceae (Philippe, 1991). In
fact, in Cucurbits, when the flowers are open, the pollen is dehiscent and the stigma receptive
for at least two hours (Philippe, 1991).
The optimal fruit yields obtained in the T1 treatment (free flowers) compared to those obtained
in the T0 treatment in the two sites are therefore attributed to the pollinating activity of the bees
on the flowers of Cucurbita maxima. According to Jean-Prost (1987), the more pollen grains a
flower receives, the more potential it has to transform into a large fruit containing many seeds;
This explains the positive and significant linear regression between the mass of the fruits
obtained and the number of mature seeds they contain. These correlations explain the fact that
efficient entomophilous pollination results in good quality fruit. In addition, poor pollination of
female flowers leads to a reduced yield and poor quality fruit. This explains why in T2, T3, and
T4 treatments, in Vogzom as in Torok, the abortion rate is high and the ripe fruits are not of
good quality (low average mass and small diameter). A good production of Cucurbita maxima
therefore depends on optimal pollinating activity of honeybees. The dependence of
Cucurbitaceae on entomophilous pollination for fruit and seed production is well established
by the results of several studies, in particular (Free, 1993; Stanghellini et al., 2002; Njoroge et
al., 2004).
From the experimental fields, a projected yield of 10.65 t/ha in Vogzom and 7.45 t/ha in
Torok was obtained by extrapolation. These optimal yields are lower than that obtained by
(Polacchi et al., 1982) which reached 5 – 40 t/ha with an average of 18 t/ha on the same species
of Cucurbita. Cordova (1990) mentions that several factors can influence agricultural yield,
including: variety, climate, cropping system, soil characteristics and the availability of
pollinators.

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Conclusion
Cucurbita maxima is a free-boding monoecious fruit of the Cucurbitaceae family. Among the
insect species recorded on the flowers of this plant species, Apis mellifera seems to have played
an important role in the pollination of Cucurbita maxima. Indeed, with a relative abundance of
around 82.06% and 40.5%, this species transported the pollen grains of the male flowers to the
stigma of the female flowers. Experiments have shown that the more a female flower receives
floral visits from bees, the more pollen grains she receives and the more fruit and seed
production is assured. Thus, the number of bee visits to the female flowers of the pumpkin
guarantees the yields of this crop. Female flowers protected from insect visits have
systematically aborted. Overall, honey bee activity conditions the fruit and seed production of
Cucurbita maxima. On farms with C maxima, the absence of bee floricultural activity leads to
zero yield.
Recommendation: Fund research to make an inventory of all pollinating insects of different
crops in Cameroon, and finally develop a reliable policy aimed at the enhancement and
conservation of the biodiversity of potential pollinators in Cameroon.
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