120 [May. 



In no feature, except u\ certain cascss in the white-marked face, 

 does the $ acquire an}^ positive 6 character of iinpoi-tance. The 

 antennae remain 12-jointed, and, in their structure, essentially charac- 

 teristic of the 2 • Perez found some slight variation in the length of 

 the joints, and thought that they indicated an approach of d and $ 

 characters. I cannot find any noteworthy change in the large number 

 of A. trlmmerana that I have examined, nor any that one could imagine 

 due to stylopization, as I have found slight variations in the antennae of 

 healthy specimens. Perez found changes in this species. Smith and 

 Hamm found no change in the case of A. nigroaenea. In cS A.fulva, 

 Avhich is extraordinarily affected b}^ Sfi/lojjs, the antennae appear to be 

 sometimes more or less affected. Where the male has quite special 

 secondary sexual organs (e. g. the form of the mandibles, their armature, 

 or that of the cheek.s), no st3dopized female has been found with these 

 characters. 



Nor do the males ever acquire any special female character, but the 

 mandibles and antennae of parasitized examples remain those of the 

 male, while poUinigerous organs are never developed. Except the colour 

 of the clypeus, they can hardly be said to lose any definite secondary 

 sexual character. Even the small basal mandibular tooth characteristic 

 of many 6 6 of the fiilva group does not appear to be lost, nor the 

 genal spine in A. spinigera. This latter case is the more remarkable, 

 since the male of the 2nd brood is normalh' without the spine or has it 

 rudimentary. 



If one places a large series of males by the side of another con- 

 sisting of females, both formed of st^dopized specimens, selecting some 

 species in which the sexual dimorphism is notable — e. g. A. trlmmerana — 

 it must be acknowledged that very rai-ely, if ever, will there be found an 

 example of one sex having such an assimilation to one of the otlier tlial 

 it would not be detected at once, if it wei'e misjjlaced. 



1. A. iiigruaenea. — There is a tendency in both sexes to a decrease 

 in the size of the head, but this is not noticeable in all specimens. 

 When the 6 bee is parasitized by a 6 Siylops the abdomen frequently 

 assumes a deeper black colour, and the long hairs on the middle of the 

 second segment become much shorter or sparser, or both short and 

 sparse ; the fourth segment and generally the third acquire a dense, 

 appressed, apical band of pale hair, more or less distinct, so as to give 

 the insect an appearance quite different from that of typical healthy 

 examples. The colour of the hair on the face of nigroaenea 6 is so 



