35G NATURAL HIS TOST. 



in concealment, have nevertheless a great diversity of needs in the matter of food. Some, like 

 the Bees, feed upon the honey and pollen of flowers ; the larvae of the Gall-flies also live upon 

 vegetable food, which is furnished to them by the tissue of the singular excrescences (galls) pro- 

 duced upon trees and plants when punctured by the ovipositors of the parent insects. Of the 

 rest, the larvse for the most part prefer animal food, at least as a portion of their diet, but the 

 form in which they obtain it differs very considerably. To some nothing seems to come amiss, 

 but the majority are more or less limited as to the kind of food that suits them. The larvse of 

 other insects and spiders are the chief sources of supply; but the mother may either collect these 

 more or less indiscriminately, or select the individuals of a single species for the maintenance of 

 her progeny. Further, besides all these cases of larva* residing in cells and fed with various 



articles collected for 



them, we find among 

 .^ the Hyrnenoptera a vast 



number of examples of 

 ^ parasitism, the females 



depositing their eggs 



LARVA, XYMI'K, AND COCOOX OF WOOD ANT (Natural Size and Magnified;. Upon Or in the body of 



some other insect, which 



then serves as the food of the larvse. The phenomena of parasitism are here displayed under almost 

 every possible variety of circumstances : the insect attacked may be in any stage of its existence, 

 from the egg to the imago ; the parasites may occur singly or several together, and their 

 emergence may take place at very different periods in the life of their victims ; but in all cases, 

 except that of the parasites in eggs, their functions would seem to be to allow the host to live 

 and perform its individual part in the world, but to prevent its leaving any progeny behind it. 

 Speaking generally, this would seem to be the most important function of parasitism in nature, 

 and it is shown very strikingly by the internal insect-parasites. 



The larvae of the Hymenoptera are provided with silk-glands opening near the mouth, and by 

 means of the secretion produced by these organs they are able to spin a cocoon for their protection 

 during the pupa state. The larvse generally remain for a considerable time apparently unaltered 

 within the cocoon, and become converted into pupae only at a period comparatively near that of their 

 emergence as perfect insects. The pupa has all its limbs and other external organs separately 

 encased and quite distinct from each other and from the body (see figure above). 



The Hymenoptera present the highest development of the mental qualities, whether they are to 

 be regarded as instinctive or as representing absolute intellectual activity, that we meet with 

 anywhere in the class of insects, or indeed among Invertebrate animals in general. It is in 

 providing for the well-being of their progeny more especially that they display these qualities 

 most brilliantly ; and although most of their actions in this direction may doubtless be referred 

 to those inherited mental operations which we usually denominate instinct, cases are not wanting 

 in which, in the presence of exceptional circumstances, these little creatures manifestly reason 

 upon the novel position in which they are placed, and adopt such modifications of their ordinary 

 procedure as may be rendered necessary. 



These intellectual characteristics, which give the Hymenoptera a pre-eminence over all other 

 insects are specially manifested in connection with another peculiarity, namely, the complex 

 social mode of life of a considerable number of the species. The extraordinary polity of the Bees, 

 Ants, and Wasps, which has excited the wonder and admiration of mankind in all ages, is only 

 partially paralleled elsewhere by the so-called White Ants (Termites), which belong to the 

 Orthopterous oi'der ; and although the proceedings of the latter are sufficiently interesting, they yield 

 in many respects to the social Hymenoptera. Fundamentally, the extraordinary social organisation 

 observable in Bees, Ants, and Wasps is connected with the care of the young, an object which appears 

 to exercise a primary influence upon the habits of many other Hymenoptera which do not live 

 in societies. It consists nof only in the living together in nests of various construction of a greater 

 or less number of individual insects, all of whom co-operate in cai'rying on the business of the 

 community, but, further, in the modification of certain individuals to fit them for the performance 



