■283 



for leaping or running very quickly ; thus dimorphism is strong- 

 ly represented amonp- Orthoptera and Auchenorhynchous Sip- 

 honata; and indeed in the Miridae, the great part of the dimor- 

 phic species have t-hickened posterior legs, as is also the case 

 with the femora in the Anthocoridae. 



(3) There are a great number of instances where the female 

 alone is dimorphic, but never a one where the male alone is so. 

 In such cases the female very often has the femora more thick- 

 ened t'han are those of the male — I among Heteropterous 

 Miridae.] 



(4) Most dimorphic species live on 'lierlis (jr near the roots 

 of such like. 



(5) On the contrary, no dimorphic species live on trees or 

 bushes. 



(6) In some cases, dimorphism depends so obviously on the 

 manner of living of the species that i't cannot be caused by the 

 climate, for example, in certain Myrmecophilous species. 



(7) Not a single dimorphic species has been found among 

 the numerous fossil Orthoptera and Hemiptera. 



Renter t^herefore concludes: 



(1) The niacropterous is the ])rimitive form and the ])rachy- 

 ]:»terous forms are only produced in a more advanced period by 

 "natural selection"; the existence of a niacropterous form of 

 a species usually brachypterous must be regarded as rcz'crsioii. 



(2) The reduction of the flight-orgaiis is probably produced 

 bv divcise causes; in certain Myrmecophanous Miridae. it evi- 

 dently depends on the manner of living of the species and 

 "mimicry"; the Anthocorid Mynncdobia colcopfrata mimics .llc.via 

 pilifcra, a little Coleopteron. [It should be noted however that 

 manv Formicicolous insects do not at all resemhle their hosts 

 or jailors.) 



(3) Manv si)ccies have lived in localities where the\- have not 

 been obliged to resort to flig*ht. because instead of trees and 

 bushes thcv have lived on the ground or among herbs, thus 

 using their legs more often. Consequently in successive gener- 

 ations, the latter are continually developed more strongly, while 

 the muscles of flight by lack of usage are generally enfeebled 

 and atrophied, the tegmina and wings thus becoming as much 

 shortened as the legs are developed and thickened, bv the law 

 of "reciprocal influence." 



(4) The male, as the active sex, has been oibliged to avail 

 himself of his organs of flight, and exercise his muscles; this is 

 why this sex, in manv species, has, by heredity, {he tegmina and 



