Laboratory of  Experimental Entomology and BioControl Theory Russia, 199034, St.-Petersburg, Zoological Institute. Phone: +7 (812) 114 0442; Fax: +7 (812) 114 0444; E-mail: rsreznik@zin.ru

The role of learning in insect host specificity

Project conducted by Dr. S.Ya. Reznik in 1980-1990.

Learning in insect host specificity (review)

Different forms of learning (habituation, sensitization, classical conditioning and instrumental learning) and the ways of its influence upon the insect behavior (feeding or egg-laying) are considered. Shortly described are the peculiar features of the methods implied in the experiments aimed to reveal the modifications of insect behavior and the sources of possible errors (the most frequent one is the influence of selection).

Learning influences upon different elements of food behavior of the insects from various orders (from Collembola and Odonata to Hymenoptera and Diptera) both phytophagous, predators, parasitoids etc. The most widespread forms of learning are habituation and the classical conditioning. The selective value of learning is the rapid and reversible (in contrast to selection) adaptation of behavior to the local peculiarities of the environment varying in time and space. Learning may accelerate and facilitate the search of food, not altering the preference. More frequently learning affects also the selectivity of feeding and egg-laying. Usually learning leads to the preference by an insect of the "habitual" food. It is achieved due to the habituation to repellents or because of the associative learning (i.e., the substitution of the contacting unconditioned stimuli by the distantly percepted conditioned ones). This is resulted in optimization of behavior due to temporary specialization on the most abundant or beneficial of all possible food.

The overwhelming majority of the insect studied more or less evidently display such type of learning, the results of which are not conducted through metamorphosis, but are restricted only to larval or imaginal stage. In Holometabola the transfer of the results of learning from larva to adult was observed far less frequently (in about 1/4 of the species studied by different authors). and seems to occur in the less advanced orders Supposedly, this should be explained not only by histolysis accompanying metamorphosis, but also by the decrease of the adaptive value of learning results transfer. The latter, in turn, is caused by the typical for Holometabola distinction in biology and behavior of larva and imago, their discrepancy in time.

The ability of insects to get learned to search for and choose the food is regarded both as the factor and as the object of evolution. The probable role of learning in sympatric speciation is analyzed, viewpoints of different authors being compared. Learning and selection are regarded as the two alternative ways of changing the food specialization. Learning is interpreted as a particular case of modification, which is not inherited, but sustaining the maintenance and spreading of heritable mutations.

References

Reznik S.Ya. 1992. Learning in food selectivity of insects. Proc. Zool. Inst. Vol. 193: 5-72 (in Russian).

Reznik S.Ya. & Gorokhova S.I. 1985. Modification of oviposition selectivity and isolation of sympatric subpopulations in insects. J. Obsch. Biol. 66, 265-270. (in Russian).