Volume 99, Issue 3
May 1990, pages 177-288
pp 177-183 May 1990
An overall analysis of the complex interrelationships involved in insect-plant interaction has been attempted with particular reference to the mechanisms of host plant searching and acceptance, nutritional and non-nutritional factors, defense systems in plants and insects and recognition systems in plants to invasion by foreign organisms.
pp 185-198 May 1990
The influence of naturally occurring toxic substances of plants such as alkaloids, rotenoids, antifeedants, growth inhibitors, hormone analogues, sterilants and antigonadial agents, on the physiology of some phytophagous insects is discussed.
pp 199-210 May 1990
The hydrogen-ion concentration of the contents of fore-, mid- and hindgut of the larva ofEarias vittella (F.) lays within a pH range of 8-8 and 9-6 These caterpillars possessed the ability to break down starch, raffmose, maltose, melibiose, sucrose and proteins. Synthesis of certain higher oligosaccharides indicating transglycosidic activity was also noticed during hydrolysis of raffinose, melibiose and sucrose inin vitro experiments. The activity of carbohydrases detected in the larval midgut was variably influenced by the hydrogen-ion concentration of the medium. Further, they differed from one another in their relative strength. Amylase was the most powerful and a-galactosidase was the weakest of all. An in vivo examination into the fate of fed starch, maltose, cellobiose and lactose within the gut revealed the physiological competency of the caterpillar to utilise only the first two carbohydrates (the former partly and the latter completely) through swiftly operating processes of digestion and absorption.
Movement of ingested food through the gut of the caterpillar was a rapid process. The first lot of food residue passed out of the hindgut within a mean time of 103 min after feeding. However, the entire alimentary canal got cleared of the ingested food only 36 h after a meal.
pp 211-224 May 1990
Importance of growing insect resistant crop in pest management programmes is discussed with reference to some of the major aspects of insect resistance in crop plants in Tamil Nadu and emphasis has been made in highlighting the fact that the plant resistance to insect should form the foundation upon which other components of the integrated pest management should be built.
pp 225-232 May 1990
Extrinsic causes affecting the performance of insect enemies of weeds including climatic unsuitability, parasitism, predation and disease pathogens are discussed, giving examples of both weeds and their insect enemies selected with special relevance to India.
pp 233-242 May 1990
The sequence of host seeking and stimuli involved in them for the larval parasitoid wasEriborus argentipilosus and its- hostHeliothis armigera are discussed through a series of experimental observations. In such a sequence of behaviour the step-by-step release of the different responses tending to contribute to the efficiency of host finding are explained.
pp 243-255 May 1990
Homeostatic mechanisms involving the regulation of the rates and efficiency of food consumption and utilization are reviewed. Adjustment in the rates and efficiencies of consumption and utilization of food during switching on from one host plant to another as well as the compensatory tactics among the consumer species are discussed.
pp 257-265 May 1990
Plant tissue culture enabling the assessment of excised organ tissues and cells and the effect of various metabolites and gall and normal tissues are discussed with reference to insect induced plant galls. In particular the stem and rachis galls ofProsopis cineraria caused by a chalcid andLobopteromyia prosopidis, stem gall ofEmblica officinalis Gaertn induced by a Lepidopteran,Betousa stylophora Swinhoe, stem gall ofZizyphus mauritiana induced by a mite,Eriophyes cernuus, thePhylloxera gall on grape and many others are discussed.
pp 267-276 May 1990
Problems of systematics and speciation in the context of recent advances in the field of insect-plant interaction are highlighted with reference to the comparative study of speciation in relation to the population structure and genetic architecture of living organisms. The role of insect-plant interaction in the biosystematic study of some aquatic weevils, aphids and archid pollinators are also discussed besides sympatric speciation in some phytophagous insects.
pp 277-288 May 1990
The well known and most useful property of the neem tree is the antifeedant property to insects expressed even in crude extracts. Azadirachtin has the highest biological activity and in addition to antifeedant property, it also produces developmental abnormalities in almost all insect orders. The chemical structure of azadirachtin has been determined unequivocally and the radio labelling opened the possibility of biochemical, metabolic and autoradiographic studies. The timing and titre of the two morphogenetic hormones are altered leading to loss of coordination of developmental events. This effect on morphogenetic hormones could be traced as the influence of azadirachtin on the neuroendocrine system which secrete the tropic hormones that eventually control the activity of corpora allata and prothoracic glands. Recent studies have shown that turnover of the neurosecretory material is poor in azadirachtin-treated insects leading to derangement of the hormonally controlled development.