MORPHOLOGICAL ADAPTATION IN INSECTS — GRAND! 219 



order to differentiate there the usual series of backward odontoid 

 microprocesses, etc.).^ 



The males belonging to group (a) (homeomorphic) are not modi- 

 fied. The males belonging to group (b) (heteromorphic) are highly 

 modified and sometimes so much so as to lose even some important 

 characteristics of the order and even of the class to which they belong. 

 Also, some of the modifications undergone are common to all the 

 members of the various taxonomic groups ; others pertain only to cer- 

 tain genera or species. Both, however, seem to be in connection with 

 determinate functions (opening of their own galls from inside, and 

 those of the females from outside, particular ways of mating which 

 compel the males to grasp at the galls or penetrate into them, etc.), 

 or the microhabitat (the inside of the receptacles), in which they 

 remain from the time of eclosion up to death — they live and die with- 

 out ever knowing the external world and sunlight. Among these modi- 

 fications (as we have previously pointed out in regard to the females) 

 we find some which seem to be of moderate use for the functions the 

 male has to perform (for instance we remember the shortening, oli- 

 gomery, and fusion of antennal joints and the concentration of their 

 sensilla in the distal end of the last antennomere or of the last group 

 of antennomeres ; the strengthening of the mandibles ; the particular 

 modifications of the thorax and abdomen), solenogastria, the particu- 

 lar shape of the 9th urite ; the strengthening of the fore and hind legs, 

 etc.) ; some of these characters seem to be the result of the involu- 

 tion or rudimentation of certain organs (atrophy of the labrum, reduc- 

 tion or atrophy of the maxillolabial complex ; reduction or disappear- 

 ance of the intergnathal cavity and its outer opening, which induces 

 the formation of "astomous" and "aphagous" forms ; involution, 

 atrophy or disappearance of the middle legs, which induces the forma- 

 tion of "tetrapod" forms ; involution, atrophy, or disappearance of one 

 pair of wings which causes the formation of "dipterous" forms, or of 

 all four wings, which gives rise to "apterous" forms ; disappearance 

 of the cerci, etc.) ; some, which conversely appear as hypertelic modi- 

 fications (a rare monstrous hypertrophy of the antennal scape, or of 

 the first or last tarsomere ; abnormal development of the head capsule 

 and mandibles, etc.) ; some which, though included at least in part in 

 the two last groups, nevertheless seem to be related to the changes 

 undergone by the organs and are considered in the first group (anten- 

 nal and tarsal oligomery ; malformations of some parts of the legs and 



5 What is affirmed above is on the basis of what we know today, and actually 

 we know very little. 



