Gillon, Yves

Louveaux, A.

Mainguet, A.M.

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FEEDING LOCUSTS ON FREEZE-DRIED PLANTS: A NEW 
REARING METHOD FOR HERBIVOROUS INSECTS 
BY 
I A. LOUVEAUX, A. M. MAINGUET and Yr GILLON 
Laboratoire d’Entomologie, Universith Paris XI Centre d’Ojsay, Bâtiment 446 
91405 Orsay Cedex, France 
The complete development and reproduction of Locusta migratoria was shown to occur using freeze- 
dried wheat seedlings as food; water being provided separately. 
This method makes the rearing of locusts easier, and allows the control of water and food intake. It 
also makes it possible to experiment at the same time on the nutritional value of plants of different 
growth stages, or plants grown in different conditions. 
In most laboratories, locusts are reared on fresh food, such as wheat seedlings 
grown on a seed-bed or with fresh cut Gramineae such as Agropyron repens, Poa 
annua, Sasa japonica, Phragmites communis, accepted by Locusta migratoria, or with 
foods such as Brassica oleracea and Lactuca sativa which may be preferred by 
Schistocerca gregaria. 
For experimental purposes dry food has previously been provided for locusts, 
but generally for a limited time (Bernays, 1977). Powdered leaf material dried at 
60°, has been added to artificial diets based on agar-agar medium (Aspirot, 1979), 
and completed with a balanced mixture of mineral salts, vitamins and proteins 
(Tira & Le Berre, 1976). 
To study the nutritional value of different maize cultivars, Anglade (1962) used 
freeze-dried food, but soaked it before being given to caterpillars of Sesamia 
nonagrioides. In this way, complete development and reproduction.were obtained. 
In experiments with fresh plants, the nutrient and water contents are difficult to 
control since these factors change quickly in the plants and from one season to 
another. Moreover, the use of dried material as food is a way of knowing exactly 
the amount of food eaten day by day. Indeed, this method is more efficient and 
precise than others habitually used such as weighing fresh food and estimating the 
water content independently, or measuring the area missing on the leaf, (Gillon, 
1970) or weighing the faeces (Louveaux, 1977). 
The variation of food quality is of importance in the case of plants grown in 
natural conditions and the nutritional value can only be investigated if the food 
~ taken stays constant in quality during the whole period of an experiment, which 
can last over a month if larval and adult development are to be investigated. 
I For these reasons and becaule one of us observed African grasshoppers eating 
256 A. LOUVEAUX, A. M. MAINGUET AND Y. GILLON 
dried material in the field, we attempted to use freeze-dried plants as food, the 
insects being supplied with water separately. The main point is to supply the insect 
with enough water. Normally, fresh food plants provide enough water for their 
requirements but in drought conditions some acridids have been seen, in nature, 
drinking free water; in laboratory rearing, locusts easily suck the wet cotton given 
to supply them with water. Locusts are known to drink in relation to their water 
requirements (Bernays, 1977). 
MATERIALS AND METHODS 
To test usefulness of lyophilised plants as food, we conducted experiments with 
Locusta migratoria migratorioides from Mali reared in the laboratory on their usual 
food, provided for 37 generations; this consists of 10 cm wheat seedlings grown on 
a seed-bed. Enough seedlings were lyophilised at the same time to feed 40 locusts 
for the whole period of the experiment. Freeze-dried wheat was kept in aluminium 
foil or in plastic bags in a vacuum desiccator. 
Newly hatched hoppers were individually separated into two groups, one group 
fed on freeze-dried wheat and the other as a control, fed with young fresh wheat 
seedlings whose water content is about 87%. Each of these groups consisting of 15 
males and 15 females was reared in a meshed cage of 3 dm3; for fifth instars we 
have done individual rearings of five males and five females in meshed cages of 0,9 
dm3. 
Mass and individual rearings on fresh and dry food were conducted together in 
the same thermoregulated cabinet at 30" with constant light and 60% r.h. 
The locusts were observed from hatching to adulthood. Water was given on 
cotton to insects which had access to dried food. To supply enough water for a 
period of 24 hr, we made a watering device which consisted of a 25 ml tube filled 
with water, turned over to damp the cotton. The dry food was not in contact with 
water at any time, The control groups were supplied with freshly cut wheat 
seedlings which were kept fresh by watering in a tube. Fresh food, freeze-dried 
food and water were renewed daily. 
RESULTS AND DISCUSSION 
Complete development of hoppers and the reproduction of adults was possible 
using freeze-dried wheat seedlings as food. 
To test the efficiency of such a food we controlled various parameters such as 
food intake, measured development length and fresh and dry weight gained, and 
we calculated the indices of digestibility and efficiencies from I.P.B. 
recommendations (Petrusewicz & MacFayden, 1970): 
Assimilatiodconsumption efficiency = A/C, 
and Productiodassimilation efficiency = P/A. 
These indices used also by the physiologists (Waldbauer, 1968) are then defined 
I 
Fresh wheat 
seedlings 
Freeze-dried 
wheat seedlings 
FEEDING LOCUSTS ON FREEZE-DRIED PLANTS 257 
TABLE I 
Percentage mortality during hopper development. 
Instars Total 
I II III IV  V mortality 
O O 16.0 % 
l5  6.6 3 6.6 O O 16.2 % 
15 o 
as approximate digestibility A.D. (= A/c) and efficiency of conversion of digested 
food to body substance E.C.D. (= P/a>. 
Mortality was the same on dry and fresh seedlings and mainly affected young 
hoppers, as is usual in rearing locusts (Table I). 
Development is slightly slower with dry food. Mean duration of development of 
the first instar was 5.4 days on fresh wheat and 6.3 days on freeze-dried seedlings 
but nymphs seemed to became adapted to the dry food since development of the 
fifth instar was almost the same as that observed on fresh food, respectively 9.2 
and 9.0 days. The adults, reared on dry food were only 3 days late after 4 weeks 
rearing. The total duration of development of the larvae was 25.6 days on fresh 
food and 28.7 on the freeze-dried food. 
TABLE II 
Growth of nymphs, data from individual rearings, jìve males, jìve females weighed on the day of ecdysis. 
Weight in mg as mean & S.E. 
Ingestion and 
during last instar 
Last instar Newly ecdysed adult assimilation of food 
PIA A/C 
8 476 ?r28 922& 33 221 f 5 76.1 773 & 27 34.6 49.1 Fresh wheat 
seedlings 0 595 f 17 1415f 26 351 f 8 76.2 1206 f 51 47.8 43.0 
Freeze-dried d 401 f 9 904 f 25 247 & 11 72.7 129 5 28 50.3 43.9 
wheat seedlings 9 570 f 27 1364 f 58 361 f 14 73.5 1206 f 31 49.0 41.2 
fresh fresh dry % dryweight 
weight weight weight H,O ingested 
Production due to body growth PIA = Assimilation 
All terms are expressed in dry weights. 
Assimilation 
Consumption 
A/C = 
258 A. LOUVEAUX, A. M. MAINGUET AND Y.  GILLON 
Females laid one to five egg pods with 50-80 eggs each in both cases. They were 
kept for a second generation. On dry food, fertility is less but no investigations 
have yet been done to find the reasons for this. 
Food intake is similar to the control (Table 11) in spite of the modification in 
phagostimulation: 
- The lack of the water which is considered as phagostimulant (Sinoir, 1968, 
Barton-Browne & Van Gerwen, 1976). 
- The eventual disappearence of leaf volatiles or “green odors” (Visser & Avé, 
1978). 
- The clamping of enzymatic mechanisms which may act as defense in plants 
(Aspirot, 1979). 
Utilisation of the freeze-dried food noted by the ratio A/c is not different from 
the controls. The ratio P/a shows that conversion of the digested food, calculated 
from individual data was somewhat variable, results being dissimilar in males and 
females. 
Feeding locusts with dry food over several weeks can greatly reduce body water 
content of the insects and their food intake, but as they have access to free water, 
they can regulate their water content (Lee, 1961). Our results showed that the 
body water content was only 3% less for the insects fed on freeze-dried food (Table 
II). 
In a preliminary test, supplying drinking water was found to be insufficient and 
resulted in cannibalism. Since locusts habitually eat small quantities of dry parts of 
the leaves they feed on, it seems better to provide water ad libitum alongside the 
dry food and allow the insect to regulate its water requirements. 
Our water supply appeared to be almost satisfactory since the whole of the life 
cycle is obtained and the differences between the treatments are not very 
important compared to the changes we had imposed on our locusts which adapted, 
and perhaps selected in our rearing conditions to food with a particularly high 
water content. Freeze drying is the best technique to preserve the nutritive quality 
of the plant and it allows a quantitative control of water since it is given separately. 
Yet we found that a small amount of water, 1.6%, is still provided with the freeze- 
dried wheat because it is slightly hygroscopic. 
This method shows that it is possible with such lyophilised food to control the 
drinking water and food intake separately, and to experiment on the nutritional 
value of plants in different conditions or ages. It may be possible to extend this 
method not only to other acridids but also to other chewing insects. 
The authors thank Mrs Hubac of the phytotron laboratory (C.N.R.S. Gif/ 
Yvette, France) for supplying the lyophilised material. Research supported by a 
grant from DGRST (contract 79.7.0259). 
‘1 
FEEDING LOCUSTS ON FREEZE-DRIED PLANTS 259 
ALIMENTATION DU CRIQUET SUR PLANTES LYOPHILISEES, UNE NOUVELLE METHODE 
D’ELEVAGE POUR LESINSECTES HERBIVORES 
Pour experimenter conjointement sur la valeur nutritive de plantes A diff6rents stades d:Cvolution, il 
a 6tB tent6 de realiser des &levages de Locustá migratoria sur nourriture lyophiliste. 
La comparaison d’individus 61ev6s depuis l’eclosion sur bl6 germ6 lyophilise a\;ec des individus 
nourris de b18 germ6 frais montre que le dessechement de l’aliment n’affecte guère ni le 
dbveloppement, ni la reproduction dans la mesure oh l’eau de boisson est fournie en quantite 
suffisante. 
Cette methode permet en outre de mesurer la consommation et l’efficacit6 de conversion de la 
nourriture ing6r6e avec bien plus de precision qu’il n’&tait possible jusqu’ici avec des aliments frais. 
REFERENCES 
ANGLADE, P. (1962). Premiers essais d’utilisation de mats lyophilisk dans l’alimentation des chenilles de 
SBsamie: Sesatnia nonagrioides Lef. (Lep. Noctuidae). Bull. Soc. Ent. Fr. 67 : 25-28. 
ASPIROT, J. (1979). Consommation par Schistocerca gregaria (Forsk) (Orthoptère Acrididae) d’une 
plante normalement delaiss6e; Pteridium aquilinum (Fougère Dennstaedtiaceae): Action de 
phagostimulants et Btude de la valeur alimentaire de la plante. ThBse de Doctorat de 3ème cycle, 
Universite Paris XI, Orsay, 100 pp. 
BARTON-BROWNE, L. & VAN GERWEN, A. C. M. (1976). Regulation of water ingestion by the locust 
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BERNAYS, E. A. (1977). The physiological control of drinking behaviour in nymphs of Locusta 
migratoria. Physiol. Ent. 2 : 261-273. 
GILLON, Y, (1970). Caracteristiques quantitatives du dkveloppement et de l’alimentation d’orthochtha 
brachycnemis Karsch 1893 (Orthoptera, Acridinae). La Terre et la Vie 24 : 425-448. 
LEE, R. M. (1961). The variation of blood volume with age in the desert locust (Schistocerca gregaria 
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LOUVEAUX, A. (1977). Capacite de r6gulation de la prise de nourriture et du dkveloppement de larves 
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PETRUSEWICZ, K. & MACFAYDEN, A. (1970). Productivity of terrestrial animals, principles and 
methods. I.B.P. Handbook 13 : 190 pp. 
SINOIR, Y. (1968). Etude de quelques facteurs conditionnant la prise de nourriture chez les larves du 
criquet migrateur, d m t u  migratoriu migratoriordes (Orthoptera, Acrididae). I .  Facteurs 
externes. Ent. exp. & appl. 11 : 195-210. 
TIRA, R. & LE BERRE, J.R. (1976). Influence d’une alimentation artificielle de type meridique sur divers 
caractères biologiques du criquet pelerin Schistocerca gregaria Forsk. C. R. Acad. Sc. Paris 282 : 
473-475. 
VISSER, J. H. & Avb, D. A. (1978). General green leaf volatiles in the olfactory orientation of the 
colorado beetle, Leptinotarsa decemlineata. Ent. exp. & appl. 24 : 538-549. 
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229-288. 
Accepted: January 12, 1980 



Feeding locusts on freeze-dried plants : a new rearing method for herbivorous insects

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