Volume 94, Issue 3
June 1985, pages 173-357
pp 173-186 June 1985
Ethology, a fast developing field of animal sciences has considerable relevance in animal husbandry, agriculture, control of animal populations, pest control, medicine, wildlife biology, etc. It has made vast strides of progress during the past few decades and some of these trends are reviewed.
Communication signals play a salient role in sociobiology of animal groups. Animals deploy visual, acoustic, tactile and olfactory signals during their social interactions. Among these, olfactory cues have certain specific advantages over the other modes concerned. Recently considerable attention has been focussed on chemical signals in animals, especially those of economically important forms such as insects, fishes and mammals.
Regarding insects, sex pheromones, aphrodisiacs, trail markers, aggregating and alerting pheromones have been isolated in various insectan orders. The factors controlling sex pheromone behaviour and impact of pheromones on control of insect population have been elaborated.
Investigations on chemical cues of lower vertebrates indicate that fishes, amphibians and reptiles deploy them in their social interactions. Pheromones modulate the schooling, reproductive and alarm response behaviour in fishes.
Among mammals, urine, fecal pellets, saliva and secretions of specialised skin glands function as sources of olfactory cues. Data on histophysiology, and ultrastructure of specialised skin glands, biochemistry of their secretions have been collected. Osmetrichia, scent marking patterns and fiehmen responses and their hormonal control have been elucidated. The neuroendocrinological basis of scent marking has been made explicit.
Relatively only very few of the mammalian pheromones have been isolated. The role of Primer pheromones in modulation of reproductive processes in some of the rodents and signalling pheromones in social interactions of some mammals have been elaborated.
Data on olfactory cues in human social interactions indicate the presence of social pheromones.
Visual signals of some insects and their role in reproductive activities have been investigated. Social postures in some rodent pests and their behavioural relevance have been studied. Acoustic signals in insects facilitate congregation, sexual attraction, aggregation and alarm responses. Further various aspects of vocalisations in birds and mammals have been investigated. Reproductive investment patterns and sex ratios in insects and parental investment in birds have been elucidated. Play behaviour and their role in behavioural development has been investigated. Etiological analysis of drug action in aggressive behaviour in certain mammals has been made.
pp 187-196 June 1985
The circadian rhythm in the process of eclosion of the fruitflyDrosophila is the best investigated with regards to properties such as entrainment, freerun and phase shifts. The system has been the basis of an important coupled oscillator model, several hypotheses, landmark papers and a monograph. ThePRC for this rhythm has been extensively used in experiments designed to test the kinetics of the basic clock. The singularity point, signifying a stimulus that can ’stop’ the clock, was also predicted and discovered in this rhythm. Fittingly the first clock mutant was also discovered inDrosophila.
pp 197-205 June 1985
Hormones play an important role in insect behaviour. These hormones are mainly the neurohormones of the brain and of the corpus cardiacum, the juvenile hormone of the corpus allatum and the ecdysone of the prothoracic glands. These produce either releaser effects or modifier effects. Hormonal modulation of neurophysiological activity controlling various aspects of behaviour, hormonal influence of reproductive behaviour in the male and the female insects, their role in migration, as well as hormonal influence of caste determination and behaviour of social insects, have been discussed.
pp 207-217 June 1985
Circadian rhythmicity in the timing of secretion and release of many of the neurohormones appears to be a common phenomenon in insects. Involvement of hormonal components in the locomotor activity rhythm in cockroaches, crickets etc. has not yet been proved unequivocally eventhough some of the findings along these lines support this. Many of the physiological events in insects occur only once in each individual’s life-time-gated events. Release of eclosion hormone in insects is determined both by a circadian clock and by the developmental competence of the insect. Periodic release ofPTTH which influence the moulting process in larvae has been established to be gated. Induction of prodromal signs of pupation as a result of gated release of PTTH in some insects have been confirmed. Intrinsic neurosecretory cells of cc release a hormone (calling hormone) in a rhythmic fashion which affect the pheromone release and subsequent initiation of calling behaviour in some of the lepidopteran virgin females. Production of proctodone by the epithelial cells of hindgut also follows a rhythm bringing about diapause in some of the insects.
pp 219-224 June 1985
Foraging behaviour of insects includes the following energy-requiring processes: (i) location and (ii) gathering. Some insects do incur additional energy cost on transporting and storing food. Energy cost of foraging ranges from 2 to 5 % of the energy gained in bees and wasps. Initiation of flight, in large and insulated insects obligatorily requires ‘warming-up’ of muscle temperature and maintenance of endothermy by over 20°C above the ambient. Over-heating is avoided by pumping the cooler abdominal blood into the hot thorax. Pollinating insects include (i) hovering high-energy foragers, which expend more energy and visit more flowers per unit time and (ii) walking low-energy foragers, which expend less energy and visit few flowers per unit time. Decreasing of “wing loading” is another strategy adopted by saturniids, which do not feed as adults. Most bees forage, when flowers are just blooming, and when they have maximum nectar reward to offer. From the model study on energy cost of oviposition, it has been shown thatSceliphron violaceum makes greater and greater effort to complete the process of food provisioning and sealing the larval nest, when it has invested more and more energy on foraging and provisioning spiders to the larviposited young ones.
pp 225-238 June 1985
The only common factor the haematophagous arthropods share among themselves is the blood sucking habit. This habit which ties them down to an unnatural assemblage, confers on them certain parallelism even in their natural diversities. Behavioural activities of haematophagous arthropods, like those of many other animals, centre around 3 major aspects: searching for a suitable host and feeding on it; meeting of the sexes and finding a suitable place for oviposition.
Behaviour of blood sucking insects assume importance because these insects act as vectors of many blood-borne infections of man and animals. In this article, feeding and reproductive behaviours of haematophagous insects are analysed on certain hierarchy of events like: motivation; search and consummation.
pp 239-247 June 1985
Feeding behavioural studies of many exclusively predatory species exhibit clearcut stimuli-response mediated sequences and these can be categorised into distinct sub-units like: search and location of prey → approach and attack of prey → immobilisation of prey → transportation of prey to safe place → consumption of prey. These feeding behavioural activities differ among reduviids particularly with respect to prey types. These bugs are endowed with many structural, physiological and behavioural adaptations for efficient predation.
The ovipositional behaviour of reduviids in different habitats also shows considerable variation and their reproductive strategies include selection of suitable sites to assure successful emergence and development of young ones and so far very few egg predators and egg parasites have been reported for these terrestrial insects.
pp 249-264 June 1985
Results of a study of certain specific environmental and physiological variables affecting the reproductive activity (specially egg yield and egg hatchability characteristics) ofCorcyra cephalonica (Stainton) (a pyralid pest damaging a variety of stored edible commodities) are considered, from a behavioural point of view, in this contribution. The environmental cues examined are (a) light, (b) population density, (c) space availability and (d) host presence. The physiological factors tested are (a) age, (b) sex ratio, (c) nutrition and (d) time of mating. The findings obtained in this investigation provide a basis to comprehend more meaningfully the complex, delicate and varied effects produced by these factors on the reproductive performance of this moth in relation to its establishment on jowar, one of the stored products naturally infested by this pest.
pp 265-282 June 1985
Various aspects of the feeding and breeding behaviours in Orthoptera with special reference to Acridoidea and Tetrigoidea are discussed. The changes in the incisor and molar mandibular surfaces, laciniae and galeae of the maxillae, in relation to graminivory, herbivory and omnivory are cited as specific manifestations of the feeding behaviour. Similarly, in sharp contrast to Acridoids the rather poor foregut armature and small and compact feculae in Tetrigoids is suggested as an evidence indicating the correlation between food and feeding habits. While describing the breeding behaviour a generalized comparison of the utilization of the acoustic sexual signals in crickets and grasshoppers causing attraction and copulation or otherwise is made. Differences in the ovipositors, mode of egg-laying and the types of eggs in Acridoids and Tetrigoids are stated as characteristic features of reproductive behaviour. Factors influencing these behaviours in Orthoptera as well as the behaviours bringing about succession and changes in the patterns of life-forms are mentioned.
Tools of behavioural investigations leading to the formulation of ethograms are briefly stated. Methods and techniques generally adopted in studying these aspects of behaviours are referred to as application of such ethological studies. The causative effect of feeding and breeding behaviours is depicted by proposing the adaptive radiation diagrams for the order Orthoptera.
The article, in conclusion, points out certain areas related to these behaviours on which, work would seemingly be useful. For example, determination of the cues that bring about mating in grouse-locusts in the absence of stridulatory and tympanal organs; the energy budget on account of their peculiar diet; and diapause are few such areas. The possibility of these forms turning out to be good models for experimental, lab-oriented studies is suggested. Since, as compared to Acridoids very little studies in the areas of economic and ecological impact in terms of population dynamics have been made on the Tettigonioids and Tetrigoids, it is further suggested that these if undertaken, would also furnish valuable information.
pp 283-294 June 1985
Though acridids are generally polyphagous, they are not indiscriminate feeders as is observed, on the basis of extensive studies on several species of grasshoppers likeEyprepocnemis alacris alacris (Serv.),Oxya nitidula (Walker), etc. The feeding behaviour of such herbivorous insects in general is of immense importance because of their direct relevance to applied ecological problems. These insects live in environments with abundance of food, but their suitability is differently related to each available plant species in the environment. Hence the feeding behaviour patterns are seen to be generally influenced by several factors such as the morphological correlates of the insect as well as the physico-chemical factors of the host plant.
In this context, consideration is being given to, (a) physical factors of the host plant such as the thickness of the leaf lamina, the presence of trichomes, the position of the leaf blade, the general colour pattern and the effect of blinding, (b) morphological correlates of the insect such as mandibular modifications in relation to the host, its changes during post-embryonic development and their role in the shift of the host, the foregut armature and its influence on host selection, (c) the influence of chemicals like silica, phagostimulants and deterrents of the hosts on the insect feeding behaviour and (d) the role of sensory structures of the insect in the detection and discrimination of the host.
In addition to the discussion on the general pattern of feeding, the factors responsible for the initiation, continuation and termination of feeding are also analysed.
pp 295-301 June 1985
During late July to early August (kharif) and late November to late December (rabi), alates ofAphis gossypii Glover appear on the old leaves of the tender brinjal plants. Population build up is quite gradual with a sigmoid growth and the pest reaches peaks during late December (kharif) and late February (rabi) when plants become mature. In course of incidence they distribute from old to young to tender leaves and the aphid incidence on these leaves is always followed by the migration of alate immigrants. Thereafter, the aphid prefers mature tissues of the crop and in course of crop maturity its dispersing trend follows from old to the other leaves as well as plants in a sigmoid posture in a latero-angular spectrum.
pp 303-308 June 1985
Social behaviour is recognised in nine families of Coleoptera. The Lamellicorn beetles, in the families Passalidae and Scarabaeidae exhibit varying types of social behaviour.
Sound production by stridulation in both the larvae and adult passalids is attributed as a social behaviour to hold the families together.
Some South American scarabs live very close to the anus of sloths and monkeys in order to oviposit on their dung. Many have association with ant nests either for food, shelter or breeding.
The dung beetles present a whole sequence of bisexual cooperation in the nesting behaviour, excavation and ball-rolling. Parental care is exhibited to a varying degree. An attempt has been made to review the feeding and breeding behaviour of Lamellicorn beetles in the light of available Indian literature including studies made by the authors.
pp 309-324 June 1985
An important feature of insect societies is the presence of a sterile worker caste that makes it possible for the fertile queens to produce a large number of offsprings. The mechanism of evolution by natural selection of such sterility and similar, though less extreme, forms of altruism has long been considered as a paradox. In recent years a large body of theoretical ideas has accumulated that purports to explain altruistic behaviour within the framework of the theory of natural selection. With special reference to insect sociality three theories namely kin selection, parental manipulation and mutualism have been suggested. Some attempts have now been made to empirically test the mutually exclusive predictions arising out of these alternative theories. A somewhat different approach to empirically distinguishing between kin selection and parental manipulation is to measure sex-investment ratios. This approach was at one time believed to have provided overwhelming support in favour of the theory of kin selection. It has now been realised that several complicating factors such as local mate competition and multiple mating have to be considered before arriving at appropriate theoretical predictions of the two rival theories. I argue in this paper that rigorous quantitative studies on inter-individual variations in behavioural strategies in primitively cusocial insects constitutes yet another approach that is likely to help in understanding the forces that mould the evolution of insect societies.
pp 325-331 June 1985
Superparasitism is frequently met with in chalcids. The actual mechanism of suppression of the supernumerary individuals is by mutual combat though exceptions to this general rule may also be seen rarely. Many chalcids are known to discriminate between parasitised and healthy hosts. It is an interesting phenomenon that superparasitism occurs even when a female is capable of discriminating parasitised and unparasitised hosts. Several factors play prominent roles in causing superparasitism and the avoidance of superparasitism by a chaicid is the result of maximisation of its reproductive success.
pp 333-339 June 1985
Seven species of moth borers are known to cause heavy losses in sugarcane production in different parts of the country. Because of their concealed habits, the control of these borers becomes complex and hence a number of methods have been tried to suppress their field population. The sex behaviour of four species of these borersviz., internode borer, stalk borer, shoot borer and top borer have been studied in recent years and among these the internode borer and stalk borer have been found to have potent sex attractants. Mass trapping may be useful in the management of internode borer while disruption technique is likely to be useful in the case of stalk borer. In both the borer species, the synthetic pheromones will be highly useful in monitoring their activity.
pp 341-350 June 1985
Under forestry conditions, management techniques aimed at maintenance of pest populations at moderate levels have greater chance of success than conventional methods of pest control. Simple behavioural observations can sometimes be used to great advantage in the development of such methods, some examples of which are given. Although there has been considerable excitement over the past two decades on the possibility of using behaviour modifying chemicals for control of pests through mass trapping or disruption of the insect’s normal communication systems, no significant practical achievement has so far been reported. Difficulties in the use of these chemicals include inadequate information on the biological responses of natural populations of insects; utilization by most insects of a complex pheromone system involving several chemical components; non-reproducibility of laboratory results under natural conditions due to several modifying factors; high cost of the development and deployment of pheromonal control systems, particularly for low value forestry crops; inadequacy of pheromonal control methods for coping with the high epidemic densities of most forest pests; and the possibility of development of pheromone resistance. Behaviour-modifying chemicals, such as food lures, sex pheromones and population aggregating pheromones, however, are useful in pest management as tools for survey and ecological research. Populations generally exhibit properties that cannot be understood by studying individual insects; study of the behaviour of populations is therefore more important than study of the behaviour of individuals for developing management strategies.
pp 351-357 June 1985
Behavioural strategies of emergence, swarming, mating and oviposition in mayflies are reviewed in the light of available literature.