MENTHA SPICATA VAR. SPICATA (L. 1753) AND RAPHANUS SATIVUS VAR.
SATIVUS (L. 1753): SURVIVAL MEAL FOR MEDAUROIDEA EXTRADENTATA
(BRUNNER VON WATTENWYL 1907) (PHASMATODEA: PHASMATIDAE)
GABRIEL OLIVE*, JEAN-YVES ZIMMER**, GILLES OLIVE*
*Ecole Industrielle et Commerciale de la Ville de Namur, Laboratoire C2A, Rue Pépin, 2B, 5000 Namur, Belgium, email:
**Hexapoda - Insectarium "Jean Leclercq", Rue de Grand-Axhe 45E, 4300 Waremme, Belgium
Medauroidea extradentata (Brunner von Wattenwyl 1907) (Phasmatodea: Phasmatidae), which was
also called Cuniculina annamensis, Clitumnus extradentatus, Clitumnus extradentata and Baculum
extradentatum (CatalogueOfLife, 2014) but remains named Cuniculina imbriga (Tedtenbacher 1908)
on Internet (Biron, 2006; OPIE, 2015; Wikimini, 2015) and at Office Pour les Insectes et leur
Environnement (OPIE) (Guyot, 2012), is commonly known as the Vietnamese or Annam Walking Stick.
Note that some authors consider Cuniculina impigra (Lelong, 1995; Busshardt et al., 2011;
Theunissen et al., 2014) as a synonym, whereas it is in fact the species Ramulus impigrus (Brunner
von Wattenwyl 1907) (CatalogueOfLife, 2015).
Medauroidea extradentata is widely bred and considered as very easy to maintain in captivity (Lelong,
1995). Although its natural food plant in Vietnam is unknown, this species is able to feed on a large
variety of plants in captivity such as brambles and raspberries (Rubus spp. (L. 1753)), rose bushes
(Rosa sp. (L. 1753)), mountain ash and nannyberry (Sorbus spp. (L. 1753)), cultivated strawberries
(Fragaria × ananassa (Duch. 1788)), cotoneasters (Cotoneaster sp. (Medik. 1789)), firethorn or
pyracantha (Pyracantha coccinea (M. Roem. 1847)), dropwort (Filipendula sp.), dogwoods (Cornus sp.
(L. 1758)), oaks (Quercus sp. (L. 1753)), eucalyptus (Eucalyptus spp. (L’Hér. 1789)), birches (Betula sp.
(L. 1753)), alders (Alnus sp. (Mill. 1754)), red and white currant (Ribes rubrum (L. 1753)), organic
lettuce (Lactuca sativa (L. 1753)) (Boucher & Varady-Szabo, 2005), common wild rose (Rosa canina (L.
1753)) (Lau, 1987), beeches (Fagus sp. (L. 1753)), hawthorn (Crataegus sp. (L. 1753)), cherry trees,
wild cherry trees and blackthorn (Prunus sp. (L. 1753)), apple trees (Malus spp. (Mill. 1754)), hibiscus
(Hibiscus spp. (L. 1753)), orange tree (Citrus sinensis ((L.) Osbeck 1765)) (Biron, 2006), hazel (Corylus
maxima (Mill. 1768)), linden (Tilia sp. (L. 1753)), chestnuts (Castanea spp. (Mill. 1754)), spindle tree
(Euonymus europaeus (L. 1753)), citrus (Citrus spp. (L. 1753)), photinia (Photinia fraseri (Lindl. 1821))
(Guyot, 2012) and ficus (Ficus benjamina (L. 1767)) (Calvin & Lange, 2010) but not ivy (Hedera helix
(L. 1753)) unlike other common stick insects as Carausius morosus (Sinéty 1901) (Guyot, 2012).
In the current management of a stick insect breeding of the species M. extradentata authors have
made some experimental observations. First, escapes of about ten young specimens (between 1-1.5
cm) among 200 young and adult insects were regularly observed. Despite the presence of succulent
plants Graptopetalum paraguayense (Walther 1938) and Aptenia cordifolia (Schwantes 1928) located
at a distance of about fifty centimeters, no escaped stick insect was found there; some of them have
however been observed on spearmint plants (Mentha spicata var. spicata (L. 1753)) located more than
80 cm from the terrarium as well as on radish leaves (Raphanus sativus var. sativus (L. 1753)) located
about 230 cm. Moreover, four live specimens at first instar (between 1.1-1.5 cm in length) were found
on R. sativus var. sativus plants shortly after mid-August 2014. How to explain this survival for fifteen
days without water or conventional food with an average temperature of 16.4 °C (AccuWeather, 2014)
The second observation was made during periods of current food plants shortage such as Rubus
idaeus (L. 1753) and Rubus fruticosus (L. 1753) (Boucher & Varady-Szabo, 2005). When M. spicata
var. spicata branches were presented, this is the stem that appeared to have been eaten ; leaves were
sometimes not even eaten. This case was observed three times and it was impossible to know the sex
and the development stage of the specimens.
All these "field" observations prompted the authors to conduct experiments in controlled conditions to
reproduce observations made in situ ; other experiments will be conducted later over a longer period in
Comm. Appl. Biol. Sci, 81/1, 2016
order to check their size compared to controls, the capacity to perform a complete cycle, … These first
experiments are described in this extended abstract. Despite all our research it seems not known to
our knowledge that the species M. extradentata is able to survive on spearmint or radish plants, or
related species such as basil or sage for the first one and cabbage or mustard for the latter.
MATERIAL AND METHODS
Experiments were conducted in Gembloux (Belgium) [50°34’N 4°41’E] in a perforated polypropylene
box of 1180 cm3 (15 cm (l) 10.5 cm (w) 7.5 cm (h)), carefully washed with green Dreft® (brand
Procter & Gamble) and thoroughly rinsed with warm water between each experiment. The stick insects
were kept at room temperature (22 ± 3 °C), the lighting corresponding to the natural light cycle and
the relative humidity was approximately 70 %. The number of specimens used in each experiment was
randomly selected by the module Study on Random of the software Gabriel Data Analysis (Olive,
2013). Stick insects were measured from the tip of the abdomen to the base of antennas with a ruler of
the Stanley brand. Medauroidea extradentata insects came from the Hexapoda breeding located in
Belgium (Insectarium "Jean Leclercq", Rue de Grand-Axhe 45E, B-4300 Waremme). Radish seeds
belong to the Excelsiorgran brand (La Hulpe, Belgium) “Rond rouge écarlate N° 0505 Saxa”.
Verification if species Medauroidea extradentata eats stems of Mentha spicata var. spicata
(September 3-8, 2014)
Three specimens (2.6, 3.8 and 4.2 cm) were placed in the presence of two M. spicata var. spicata
branches growing in interior pot, the first plant dating from 2001. Each day the two spearmint
branches were replaced by two new ones, one in the morning and the other in the evening. Some water
(0.2 ml) was added in the morning of the third experiment day, directly on the bottom of the box in
order to ensure the stick insects survival. This complete experiment lasted five days.
Survival on leaves of Raphanus sativus var. sativus (September 20 to October 18, 2014)
Eleven specimens - between 1.1 and 1.5 cm in size - were placed in a box containing two leaves of R.
sativus var. sativus, of which the petiole is kept in water by a safelock microtube (2 cm3 in capacity);
the cap of this microtube was perforated in order to supply water to leaves, without allowing access to
stick insects (fig. 4). Seeds of R. sativus var. sativus were planted 4 months before the beginning of the
experiment. The two leaves of radish were changed at the 5th, 8th and 12th day. The 15th day, R.
sativus var. sativus leaves were replaced by two leaves of Rubus idaeus that were changed the 5th, 8th
and 12th following days. A wet sponge was also introduced in the box during the second phase of the
experiment which also lasted 15 days.
RESULTS AND DISCUSSION
It is well known that in captivity Medauroidea extradentata species mainly feeds on bramble (Rubus
fruticosus), raspberry (Rubus idaeus) (Rowley & Ratcliffe, 1980; Lelong, 1995; Boucher & Varady-
Szabo, 2005) or hazel (Corylus maxima) (Guyot, 2012). During a winter while it was difficult to find R.
idaeus and C. maxima leaves, feeding trials were conducted with spearmint (M. spicata var. spicata). It
was observed that insects had eaten spearmint stem instead of leaves. To confirm this observation a
controlled experiment was conducted consisting to put three stick insects (between 2.6-4.2 cm in
length in order to be big enough to eat stems) in a box with two branches of M. spicata var. spicata.
Each day the two spearmint branches were replaced by two new ones, one in the morning and the
other in the evening. The fourth day eaten spearmint leaves were observed (fig. 1) and the 4.2 cm
specimen was photographed while eating leaves (fig. 2). The next day the proof that M. extradentata
stick insects are able to feed on spearmint stems (without consuming the leaves) could be observed
(fig. 3). To date no plausible explanation has however been found to explain the fact that in some cases
stick insects prefer the stems to the leaves. To our knowledge no studies on the chemical composition
of the leaves and stems have been performed on M. spicata (Baser et al., 1999; Chauhan et al., 2009;
Orio et al., 2012) unlike Mentha pulegium (L. 1753) (Cook et al., 2007). Despite their chemical
proximity, these results cannot be extrapolated because the major compound for M. pulegium is
pulegone (Cook et al., 2007), while it is carvone for M. spicata (Chauhan et al., 2009). In the case of M.
pulegium, the stem contains 20 % less pulegone than the leaves (Cook et al., 2007); this may be an
explanation that the stems of M. spicata contain less carvone than the leaves. But the most likely
hypothesis is that the M. spicata stem contains little essential oil, as in the case of M. pulegium (less
than 0.1 % on dried stems (Cook et al., 2007)) ; the first hydrodistillation trials (for a gas
chromatography analysis) tend to confirm this hypothesis. Note that in the presence of bramble,
raspberry or hazel foliage, stick insects are not interested in spearmint branches.
In August 2014, after fifteen days without current food (bramble, raspberry and hazel) and water, four
specimens of approximately 1.5 cm in length were found on radish plants (R. sativus var. sativus). No
plausible explanation has been found except the fact that the four insects had probably survived by
eating radish. For this, eleven specimens - between 1.1-1.5 cm in length in order to be closer to the
four survivors - were only placed in the presence of radish leaves, without access to water, to test as
closely as possible the hypothesis. The third day one specimen ate a small piece of leaf, the missing
piece being only visible with a magnifying glass. Figure 4 shows the 11th day of the experiment, stick
insects eating the leaves that have been attacked from the 9th day. The first death was recorded on
the seventh day and from there, there was almost one death per day for a total of 7 on the fifteenth
day, the last day of the first experiment phase. The remaining four specimens were then replaced in
normal living conditions, that’s to say in presence of water and only fed on wild raspberry for a period
of fifteen days, with changes of leaves based on the same frequency that the first phase. From the
beginning, the surviving specimens drank and ate raspberry. At the 6th day of the second phase, a
new death was confirmed. After fifteen days, there were so three survivors measuring respectively 1.5,
1.5 and 1.8 cm. Although no moult has been observed, the three specimens had probably to moult
during the second phase of the experiment (in the presence of raspberry). It seems that the tested
hypothesis is confirmed, that’s to say that a small number of M. extradentata are able to survive on R.
sativus var. sativus plants, even if radish leaves are not eaten in the presence of raspberry.
Figures 1-4. Results of experiments. 1, eaten spearmint leaves (Mentha spicata var. spicata) ; 2,
female stick insect eating a spearmint leaf ; 3, eaten spearmint stem ; 4, young stick insects
eating a radish leaf (Raphanus sativus var. sativus). Photos 2 and 4 were treated with a filter of
color revitalization (Altalux/Irfanview) to increase sharpness
In case of usual food shortages (bramble, raspberry and hazel), it has been demonstrated that some
specimens of the species M. extradentata are able to survive on other food resources. Mentha spicata
Comm. Appl. Biol. Sci, 81/1, 2016
var. spicata does not seem to pose adaptation problem (ongoing experiment), but survival on R. sativus
var. sativus is obviously accessible to a limited number of specimens (3 out of 11 in this experiment).
This is the first time that it is observed that M. extradentata is able to feed on spearmint and radish.
These experiments will be repeated over longer periods in order to study if specimens living on one of
the cited plants have the capacity to perform a complete cycle, if their eggs are viable, and also to
check their size compared to controls. In addition other plants will be tested.
The authors are grateful to Matthieu Alderweireld (Gembloux Agro-Bio Tech, Université de Liège, Unité
Gestion des Ressources forestières) for help with precise identification of some plants.
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