THE INSECTS 2975 



the attendants on a preparation of pollen or other foods specially prepared. In 

 other cases the eggs may be laid on the foliage of trees and plants on which the 

 larvae feed, or they may be deposited upon or in the bodies of living or paralyzed 

 caterpillars, grubs of other species, or spiders, locusts, and the like. The Cynipidce 

 with the poison from their sting, and other causes combined, produce a large gall 

 upon the leaves of trees, especially oaks; and on the fleshy cell structure of these 

 galls the grubs feed when they emerge. Larvae of two different kinds are met with 

 in the order. Thus, whereas those of the sawflies have legs, sometimes even more 

 in number than those of the Lepidoptera, the grubs of the majority lack functional 

 legs. The former live a life of greater liberty, feeding on the foliage of trees; the 

 latter are free, so far as they are not confined within an egg membrane, but being 

 internal feeders, whether in foliage larvae, wood, or shut up as solitary her- 

 mits, each in its several cell passes a larval period of limited freedom. It is a curi- 

 ous fact that the legs of some larvae are more evident in an early than in the latter 

 stages, thus proving that the habit of cell life is a comparatively recent departure 

 from a former habit, when in all probability the larval life was passed in greater 

 freedom. 



The phenomenon of parthenogenesis is one which crops up in vari- 

 ous orders of insects, being simply the production by the female of 

 eggs or young without the fertilization of the egg germs within the female, by the 

 stimulative elements necessary to the production of young in the higher animals. 

 It is not, however, a chance phenomenon, appearing as a race-preserving expedient, 

 on the sudden failure of male forms, but one of nature's resources for preserving the 

 continuity of species. It is constant in many species of the Hymenoptera, in the 

 form of what is known as the alternation of generations; in some species, however, 

 it is supposed to be the sole form of reproduction, for the males of these species 

 have never yet been discovered. Whether we regard the fertilization of the female 

 egg germs by the male elements as dynamic or stimulative, or as merely a matter 

 of the interchange of character determinants between the two sexes, it appears to be 

 beyond a doubt that a continuous succession of virgin reproductions must inevita- 

 bly tend to the degeneration and ultimate extinction of the race. Parthenogenesis or 

 virgin reproduction may be of three kinds: First, resulting in the production of the 

 male sex only; second, of the female alone; and thirdly, in cases when the young 

 are produced not as eggs in the first instance, but alive, as in the case of the plant 

 lice or Aphides. It seems that parthenogenesis does not favor the production of one 

 sex more than another. We should, therefore, be cautious how we accept too 

 hastily the commonly received belief that male bees are necessarily the offspring of 

 nonfertilized eggs. It by no means follows that because an egg was not fertilized 

 that therefore the sex produced in it is the direct result of nonfertilization. The 

 question, however, is still a matter of controversy, and more evidence is needed be- 

 fore final conclusions can be reached. 



That the members of this order are on the whole useful to man cannot be 

 doubted, more useful perhaps than the majority of insect forms, whether as 

 bees, with their honey-storing instincts, or as the ichneumon tribes dealing destruc- 

 tion to thousands of the larvae those insect pests which would otherwise work 



