Volume 96, Issue 3
May 1987, pages 153-347
pp 153-169 May 1987
InEarias vittella (F.) (a major noctuid pest of malvaceous crops) changes in the larval food quality (developing seeds, mesocarp, epicarp of okra fruit or the entire fruit; ovary of shoeflower) in either or both sexes led to pronounced disparities in the reproductive performance of the emerging moths. Highest breeding potential was observed when males and females obtained their nourishment, during postembryonic period, from developing seeds of okra of 0–8 days old and such nutrition must be made available for the caterpillars at least for the first 3 days of their lives to attain enhanced level of reproductive efficiency later as moths. During adult life, a carbohydrate nutrient was mandatory for these mated females to realize full fecundity which got tremendously boosted when the sugar was raffinose.
Appreciable increase in ovarian weight with marked improvement in oviposition occurred inTribolium castaneum (Herbst) (a serious tenebrionid pest of cereals and other plant-derived stored commodities) when both larvae and adults ate whole flour instead of semolina, both enriched with yeast. This became further augmented when the flour ingested by these beetles during adult life was previously extracted in 100% ethanol and then reinforced with yeast. However, whole wheat flour or yeast alone given as food to such reared adults caused a sharp fall in the egg deposition of females. Number of eggs laid by mated females also differed considerably when their imaginal diet consisted of one of certain selected nutrients, oilseeds or spices—all supplemented with yeast. Egg hatchability was always 100%.
pp 171-179 May 1987
Food consumption and fecundity of insects vary with life style and feeding pattern. In general, species which feed during the larval and adult stages and maintain a smaller biomass, allocate a higher percentage of the ingested energy to egg production (e.g.Oryzaephilus surinamensis; 34.4%). Species which grow larger but feed at lower rates and pass through extended adult life span display very low egg production efficiency (e.g.Poecilocerus pictus: 0·7%). A few others feed at faster rates during the larval period, shorten the adult phase and allocate fairly a high percentage of the ingested energy to egg production (e.g.Bombyx mori; 5·8%). Food quality regulates food consumption and thereby significantly influences egg production in several polyphagous insects. Prey density influences food consumption and fecundity of predators. Regression of fecundity on blood meal ingested for two hemipterans and two dipterans revealed that the dipterans are autogenous and are relatively independent on adult blood meal for oviposition in comparison with the hemipterans.
pp 181-184 May 1987
The essential polyunsaturated fatty acids required by insects in their food appear to be needed for prostaglandinogenesis. Prostaglandins themselves are likely to be widely distributed in insects playing perhaps an hitherto unsuspected important role as in reproduction.
pp 185-193 May 1987
In acridids during feeding, the central nervous system receives information through sensilla which in turn integrated incoming information giving the appropriate motor output. Hormones and haemolyph factors like osmotic pressure also limit meal size. In the red cotton bug,Dysdercus cingulatus hormones from the neurosecretory cells of the brain induced feeding and the protein food ingested in turn stimulated midgut enzyme production while juvenile hormone has little influence either on feeding or enzyme production. In lepidopterans both brain hormone and juvenile hormone seemed to stimulate feeding and the amount of food ingested induced enzyme production. Midgut endocrine cells have also been demonstrated in several lepidopteran species.
Reproduction involving vitellogenesis, spermatogenesis, oviposition, accessory glands activity and mating behaviour is also under the regulatory control of several hormonal principles such as juvenile hormone, ecdysone, oostatic hormone etc. However, a detailed analysis of the literature available on the topic reveals that these regulatory mechanisms are tissue and species dependent.
pp 195-206 May 1987
Seed host diversity and subsequent impact of the nutritive value of different malvaceous host plant seeds determined the life-history consequences and the seed-use pattern of the dusky cotton bug,Oxycarenus laetus Kirby. Significant differences were observed in the feeding, food utilization and reproductive success of the bugs depending upon the type of seed food utilized as well as its biochemical profile particularly proteins, nitrogen, carbohydrates, phenols and lipids. Analysis of the different life-table statistics such as developmental time, maturation time, net reproductive rate (Ro), and the intrinsic rate of increase (rm) revealed seeds of crop plants to be better utilized when compared to malvaceous weed hosts.
pp 207-215 May 1987
The influence of leaf age on the quantitative food intake and the reproductive success of the cucurbit specialistRaphidopalpa atripennis F. is provided. The host plant influence on the adult longevity and survival percentage were also studied. The differential feeding behaviour and the relative preference of this beetle towards mature leaves and better reproductive success are attributed to the chemical composition of the host leaf. The individual fatty acid profile of the various hosts as well as the different leaf ages is also attempted.
pp 217-220 May 1987
Observations on the fecundity ofMylabris pustulata maintained on two different food plantsIpomoea cornea andIpomoea tuberosa, with males and females reared separately on the flowers of these two host plants are discussed.Mylabris pustulata reared onIpomoea cornea laid 144±30·80 eggs while that onIpomoea tuberosa only 93±38·87 eggs. The chemical composition of the flowers ofI. cornea andI. tuberosa revealed that protein concentration is greater inIpomoea cornea (4·88%) thanIpomoea tuberosa (4·64%). The quantity of food ingested is also greater when reared onIpomoea cornea (1055 mg). In the light of these observations it is presumed that the food rich in protein concentrations is among the principal factors influencing fecundity.
pp 221-227 May 1987
Callosobruchus maculatus was reared onVigna unguiculata, Phaseolus radiatus andDolichos lab lab from hatching to death at 20, 25, 30 and 35°C. Food consumption, growth and egg production were estimated in terms of energy. At the tested temperatures, host seed species significantly influenced feeding and energy allocated to egg production. Irrespective of the seed species, food consumption decreased with increasing temperature. Energy density of an egg did not vary with seed species but significantly decreased with increasing temperature. Fecundity (egg/females) ofCallosobruchus maculatus ranged from 73 onD. lab lab at 35°C to 118 onVigna unguiculata at 30°C. Energy allocated to egg production at 20°C was more than at other temperatures. A statistically significant inverse relationship exists between overall feeding rate ofCallosobruchus maculatus and energy allocated to egg production.
pp 229-237 May 1987
Comparative analysis of the effect of different natural host plants on the nymphal duration, quantitative food utilization and fecundity of two species of acridids,Aiolopus thalassinus (Fabricius) andGesonula punctifrons Stal revealed significant differences that were attributed to the varied nutritive value of the host plants.Aiolopus thalassinus appeared to show greater preference forPanicum maximum andCyperus rotundus as againstCynadon dactylon andCoix lachryma. SimilarlyGesonula punctifrons showed greater food intake and fecundity onEichhornia crassipes andColocasia sp thanMusa paradisiaca andIpomoea sp. Various growth parameters such as consumption index, approximate digestibility, growth rate, efficiency of conversion of ingested food and digested food were also analysed for the study of the nutritional impact in addition to the biochemical profile of the host plants.
pp 239-244 May 1987
Brinjal (solanum melongena Linn.) leaves of varied maturity show a remarkable variation in respect to the retention of nutrient contents therein. The contents also vary along with the increase of plant age.Aphis gossypii Glover, an important pest of the crop, shows high reproductive potential on old and young leaves when the plants are young (2–4 months old) and mature (4–6 months old) respectively. Amongst the nutrient content of the leaves, nitrogen level shows a significant correlation with the reproductive potential of the aphid species leading to its population outbreak and niche selection.
pp 245-251 May 1987
The survival and fecundity of the scale insect,Melanaspis glomerata (Green) varies according to the sugarcane varieties on which they feed. When the sugarcane setts infested with scale insect crawlers were maintained on different nutritional bases, high survival and fecundity were observed in distilled water as the medium. The nutrition of immature stages and adults of the egg parasite,Trichogramma spp. was found to influence the longevity and reproduction. The eggs ofCorcyra reared on groundnut kernels had appreciable quantities of growth promoting amino acids like glysine, analine and tyrosine and this influenced the size of the adult parasites. The higher fecundity of the parasites obtained from the eggs ofCorcyra reared on greengram was attributed to the maximum level of nutrients. The individuals which emerged from superparasitized eggs showed reduction in mating and fecundity because of the sharing of the nutrients. The adult longevity and fecundity increased when fed with different sugars in the presence of host eggs. Increase in the protein content in adult diet decreased the fecundity.
In the larval parasite,Sturmiopsis inferens the qualitative variation in the nutrient contents due to interspecific variation and quantitative variation as influenced by the size of the host influenced the reproductive capacity of the parasite.
pp 253-273 May 1987
Hosts of haematophagous arthropods range from amphibians to mammals. Blood meal is essential for egg production. Quantity and quality of ingested blood are important in realization of optimum reproductive potentials. In terms of egg production, the lowest nutritive value is for human blood. This inequality is probably based on differences in proteins and their constituent amino acids. Carbohydrates in the diet have no direct contribution to reproduction. Very little is known about sterol, lipid, vitamin and salt requirements for reproduction. In the mosquitoAedes aegypti some substance from the blood meal is thought to initiate vitellogenesis and is sustained by a complex hormonal mechanism in which median neurosecretory cells, corpus allatum, fat body and ovary participate. Mechanical stimuli from gut distension also has a role in hormone induction.
Autogenous egg production seen in many dipterans is controlled both by the nutrition of the immature stages and genetic mechanisms.
Quantity and the rate of utilization of the ingested blood decide the frequency of host visitation and feeding. Vertebrate blood sera contain substances which stimulate (secretogogue) as well as inhibit digestion. Nutrition plays some role in male maturation in insects, though not in spermatogenesis. In many ticks even spermatogenesis is influenced by adult blood meal.
pp 275-280 May 1987
Mosquitoes depend on high fecundity to compensate for heavy immature mortality. Important factors affecting fecundity are (1) Body size, dependant on larval nutrition (2) Amount of blood ingested (3) type of blood ingested. With the development of highly sensitive techniques for determination of bloodmeals of wild mosquitoes many puzzling variations in host selection behaviour are now capable of explanation.
pp 281-291 May 1987
Two species of polyphagous parasitoids,Gryon sp andTelenomus lucellus, parasitising the pentatomidsAcrosternum graminea andAgonoscelis nubila were subjected to host preference studies and consequent impact on the rates of parasitism of these host eggs. Chemical composition of these eggs were correlated with the age specific fecundity of the parasitoids. Polyphagous pentatomids likeAcrosternum graminae had varying fecundity on different host plants likeCleome viscosa, Gynandropsis pentaphylla, Leucas aspera, Croton sparciflorus, Acalypha indica etc and this variation was found to depend on the chemical parameters of these host plants. The overall egg output of the pentatomids was also found to influence the percentage of parasitism.
pp 293-304 May 1987
Impact of predation and food utilization on reproduction of the water bugs —Diplonychus indicus andRanatra filiformis was studied. InDiplonychus indicus, the food quality affects the rate of predation as well as food utilization. Allometric growth of various body parts and the longevity of each nymphal instar of the bug showed distinct variation, when exposed to individual prey item vizCulex, Anopheles andAedes larvae and fish fingerlings. InRanatra filiformis, a distinct pattern of oviposition in relation to the increased rate of predation onCulex larvae was observed. The significance of such variations in reproductive activities of these water bugs was discussed.
pp 305-309 May 1987
The relative importance of organic detritus and algae in promoting the growth and fecundity of some species of Baetidae is assessed on the basis of the nutritional differences among them. Taking into consideration the ephemeral aspect of adult life, an understanding of the relative importance of such substances as carbohydrate, protein and lipid in relation to their growth and fecundity is also examined.
pp 311-316 May 1987
Pest control is today an important segment of entomology supported by objective programs of research, education and business management. In the continuous search for newer strategies for pest suppression, certain unique ideas have emerged and concretized to definite principles and practice. The two themes which merit relevance and recognition here are the use of chemicals directed to interfere with feeding and reproduction in insects. The impact of chemicals derived from natural and synthetic sources has been well utilized by entomologists to suppress pests effectively either by inhibiting the gustatory stimulus or the reproductive potential.
pp 317-321 May 1987
Tiger beetles belonging to the family Cicindelidae are exclusively predaceous and have great impact on the natural eco-balance. Recent studies have revealed the existence of more than 300 species all over India under divergent habitats and none have been exploited for biological control of insect pests. Studies on the impact of differential feeding on the reproduction ofCicindella cancellata revealed a definite relationship between the quality and quantity of food consumed by adults on the fecundity, egg size, longevity of the adults, larval emergence pattern and the survivability of first instar larvae.Corcyra cephalonica larvae fed 3 times a day (55·74 mg) resulted in maximum egg production, longer adult life and longer survival of first instar larvae, followed by Corcyra, one larvae per day (37·16 mg) and mixed food of spiders, hoppers and Corcyra (alternately) 32·81 mg). Least fecundity was observed when fed with ants alone and no eggs with no food.
pp 323-327 May 1987
The correlation between nutrition and reproduction with reference to two grouse locusts,Euscelimena harpago (Tetrigidae: Scelimeniae) andPotua sabulosa (Tetrigidae: Cladonotinae) is assessed. As far asEuscelimena harpago is concerned the impact of nutrition on reproduction is presented with reference to ovarian development in certain nymphal stages and in the adult. On the other hand, the impact is evaluated from an altogether different angle as far asPotua sabulosa is concerned. This pigmy locust prefers moss as food and tides over winter and hazardous summer as adult. During this period it almost does not feed. This peculiar feature is used as a parameter to assess the nature of impact inP. sabulosa.
pp 329-332 May 1987
The present study aims to understand the influence of biochemical parameters of the host plants vizAbelmoschus esculentus L.,Gossypium hirsutum L. andAbutilon indicum G. Den. on the reproductive biology ofEarias vittella. The results indicate remarkable variation in the biochemical parameters of host plants which affected significantly the growth index and reproductive potential of the insect species. Decrease in body weight, fecundity, prolongation of larval period, percentage of larva becoming adult and adult longevity of both male and female was observed when reared onAbutilon indicum which had less amount of reducing sugars, protein and free amino acids but had high amount of non reducing sugars. Decreased larval period, increased fecundity and adult longevity were observed when reared on cotton and okra which had high amount of reducing sugars, free amino acids and protein. There was no significant difference in the amount of total soluble sugars among the 3 hosts tested. The growth index and fecundity ofEarias vittella are apparently high on okra than on cotton. It is observed that high amount of reducing sugars, free amino acids and protein seems to be favourable for increase in fecundity ofEarias vittella.
pp 333-340 May 1987
Pattern of energy allocation for reproduction was studied as a function of feeding regimes in the silkwormBombyx mori. The larvae were restricted to feed for 6, 12, 18 or 24 h (ad libitum). Restriction of feeding duration resulted in slow growth and extended larval duration. Consumption, assimilation, conversion and metabolism and their rates showed steady increase with the increase in the feeding duration. On pupation, energy allocation for egg production was studied by dissecting the pupa and estimating the reproductive and body tissues separately during the entire pupal period. Length and biomass of ovary steadily increased with increasing feeding duration as well as with increasing age of pupa. During egg development, the tissue protein was transferred to the ovary. This type of conversion was more in those fedad libitum than in those restricted to feed for shorter durations. Tissue fat and ovarian fat decreased as a function of age of pupa, indicating that fat served as the main source of energy for pupal metabolism.Bombyx mori restricted to feed for 6 h duration allocated 55% pupal energy for reproduction while those fedad libitum allocated about 67% of the pupal energy for reproduction. However, they allocated about 15–19% of assimilated energy for egg production in all the feeding regimes.
pp 341-347 May 1987
Neem extracts and pure azadirachtin influence the behaviour and physiology of large number of insects. These compounds affect the sensory receptors, thereby inhibit food intake. This anti-feedant property is exploited by using neem extracts and azadirachtin for plant protection. The gut motility and movement of food in the digestive tube are regulated by azadirachtin.Holotrichia serrata, the beetle of the ‘white grub’ feeds on neem leaves and no ill-effect of azadirachtin is reported.
Azadirachtin and neem extracts regulate the reproductive functions of insects through their endocrine system. Morphogenesis, ovarian development, fecundity, egg viability and moulting are adversely affected by azadirachtin. Radioimmunoassays show that the ecdysteroid level falls drastically on azadirachtin treatment. Juvenile hormone synthesis also is inhibited inLocusta on administration of azadirachtin. InOncopeltus fasciatus, high doses of azadirachtin inhibit adult development resulting in permanent larvae which show oocyte differentiation with yolk incorporation equivalent to day 4 of adult development.