E fleets of Castration ni Insects 385 



joint. In the stvlopized male of this species Perez found the sec- 

 ond funicular attaining to two-thirds the length of the third joint 

 and to this extent approximating to the conditions in the female. 

 (5) The normal female Andrena bears a fringe o long hairs, the 

 ana fimbria, on the edge o the fifth adbominal sternite, but th s 

 fring ; s lacking in th normal male. St\ lopization tends to sup- 

 press the development of the fimbria or causes it to disappear com- 

 pletely in the female and more rarely has the reverse effect on the 

 male. (6) The sting, which is peculiar to the female, is reduced in 

 size in the parasitized individuals, the copulatory organ of the 

 male is also reduced in length and becomes narrower and less 

 curved, while the paramera tend to become atrophied. 



Perez concludes from these observations that, so far as the 

 secondary sexual characters of Andrena are concerned, the modifi- 

 cations induced by the Stylops are not merely attenuations, but 

 actual inversions of development. "The stylopized Andrena, 

 male or female, is not merely a diminished male or female; it is 

 a female which takes on male attributes; a male that takes on the 

 characters of the female." 



The intimate correlation which exists between the structure and 

 instincts of all organisms, leads one to look for instinct peculiarities 

 corresponding with the morphological inversions described above. 

 Perez found onh' one stylopized female Andrena which had its 

 hind legs charged with pollen, and he therefore concludes that the 

 stylopized bees rarely or never forage or build nests like the normal 

 females. Normal and parasitized bees of both sexes, however, 

 visit flowers as this is not a unisexual instinct, and hence the 

 triungulins produced by 'the Stylops have an opportunity to 

 move off onto the plants, climb onto normal foraging bees and 

 thus get transferred to the brood in incipient nests. In this way 

 the perpetuation of the parasites is insured through a line of bees 

 capable of nourishing them. 



The internal changes due to stylopization have been studied by 

 Newport (48), Perez and Perkins (92). All of these authors 

 find that the testes and ovaries are not destroyed by the parasite 

 but are more or less reduced in size, in the male sometimes only on 

 the sideof the body bearing the Stylops. In the female the oocytes 



