1921] The Age of Insects 43 



least interesting is the small size of many of the forms. This is especi- 

 ally true of some of the egg parasites which are among the smallest 

 known insects. Imagine an insect small enough to pass all of its 

 stages in an insect egg not much larger than the period in ordinary 

 newspaper print and you will have a proper conception of their size. 

 Then when you remember that each adult is furnished with a pair of 

 eyes and a pair of antennae, three pairs of legs and two pairs of wings, 

 with mouth parts and a digestive system, with a nervous system and 

 sense organs and is endowed with instincts enough to feed on the nec- 

 tar of flowers and to mate and to lay eggs in the proper host at the 

 proper time; and all this in an insect not over }^ mm. long or so small 

 that one hundred of them placed end to end just equal an inch; with 

 these facts all before you you will have a proper conception of the 

 marvelous ability of nature. 



I cannot pass the subject of parasitism without mentioning two 

 special phases of insect parasitism, polyembryony and hyperparasi- 

 tism. Polyembryony is that condition in which one egg gives rise to 

 more than one adult individual. It is known to occur in many groups 

 of the animal kingdom, for example, the identical twins of man and 

 other mammals, the quadruplets of the armadillo and others. But 

 this condition reaches its greatest development among insects where 

 Patterson reports not less than 395 individuals from a single parasitic 

 egg. 



Hyperparasitism is even more wonderful than this for here we have 

 the case of one parasite preying upon another. We have not only the 

 primary parasite which preys upon the host but a secondary parasite 

 preying upon the primary parasite and a tertiary parasite upon the 

 secondary parasite and apparently in rare cases a quarternary parasite 

 preying upon the tertiary. Can anything more involved be imagined? 

 And can man ever hope to unravel the intricacies of the relations that 

 must exist in such elaborate cases of hyperparasitism? 



Ecological Relations. 



The realm of ecology is as broad as the sum total of all of the factors 

 that touch an insect during its hfe. It is therefore not surprising that 

 we know so little about the ecological relations of insects. The tem- 

 perature relations are perhaps the only ones that have been investi- 

 gated with any degree of thoroughness and here our firm ground con- 

 sists of a series of critical high and low temperatures for a few economic 



