92 Annals Entomological Society of America [Vol.11, 



The wingless males are interesting types of degeneration 

 (Fig. 3). They have not only lost their wings, but the thoracic 

 lobes are also disappearing. In most specimens of about a score 

 examined these structures are distinctly traceable, although re- 

 duced, and compare well with those of any winged form of the 

 genus Aphis; but in some individuals they are degraded to mere 

 vestiges in the shape of irregular dusky marks. In these more 

 degenerate specimens only the ocelli, present in all winged aphids, 

 prove that they were, until comparatively recently, winged 

 insects. In this species we may hope to find occasional males 

 still retaining their wings. Weed has shown that both w^inged 

 and wingless males occur in Cladobius salicis L., and Gillette 

 has found both forms in Aphis torticauda Gillette. No winged 

 males of Aphis atriplicis were found this fall, although I kept this 

 possibility constantly in view. On October 15 th I did find three 

 winged males in copulation w'ith females of this species, but the 

 males could not possibly be the same species, for they w^ere gener- 

 ically distinct. This observation suggests the possibility of hy- 

 bridization in the plant lice. Weed in 1891 observed the copu- 

 lation of a male of Cladobius salicti Harris w4th a female of Lachnus 

 platanicola Riley. These records also teach us that the mere pairing 

 of two plant lice does not prove their specific or generic identity. 

 The former can, however, be safely inferred when many males 

 are found pairing with a large number of females possessing 

 similar structural characters. 



The wingless males of a red Myziis (?) on cherry (not Myziis 

 cerasi Fab.) collected at Forest Hills last fall, have degenerated 

 much farther than those of our Chenopodium aphM. Here all 

 traces of thoracic lobes have disappeared, and the ocelli are scarce- 

 ly discernible. A still farther step in degeneration has apparently 

 taken place in the wingless male of the corn-root aphis {Aphis 

 maidi-radicis Forbes), if we may judge from Forbes' figure and 

 the descriptions by the same writer. Weed, and Davis, in which 

 no mention is made of the ocelli. There w^ould be no way of recog- 

 nizing this male as a descendant of a winged male ancestor were it 

 not for these intermediate forms, which I have discovered. This 

 process of reduction of structures correlated with the organs of 

 flight is an instructive illustration of what must have occurred long 

 before in the evolution of the wingless vivipara, which has even 

 lost all traces of ocelli. These facts also suggest the probability 

 that this female in the Aphididce is not a case of paedogenesis as 



