1892.] 41 



they could never find an exit. The two ^s were also of no repro- 

 ductive use, although the external appearance of the testes and vesiculce 

 seminales was normal ; but no signs of the curious spermatozoa were 

 to be found in any stage of formation ; the ductus ejaculatorius was 

 nearly solid throughout its whole length. 



The M-all of the alimentary canal under the parasites was ex- 

 tremely thin ; this is no doubt due to the parasites, which gain their 

 nourishment by osmosis from the digestive tract of the host. 



The reason of the large size of these stylopized bees is simply 

 this, the extra nourishment taken by the parasite or parasites necessi- 

 tates the enlargement of the digestive and secretory organs, and as 

 this can only take place in a ventral direction, it causes abnormal 

 pressure on the sexual organs, which causes their abortion. 



As to the number of parasites in each host and the proportion of 

 sexes infected, the two tables, taken from many I have (all tending 

 to the same conclusion), show that the ? s suffer most from the attack, 

 as Shuckard says, and also that one parasite to each host is the 

 general rule. 



Andeena lapponica. Andeena nigeo-s:nea. 



54 specimens. 40 specimens. 



2 ?s with 3 Sti/Iops. 3 ?8 with 3 Stylops. 

 6 ?8 „ 2 „ 1 <? „ 3 „ 



3 <?8 „ 2 „ 3 ?8 „ 2 „ 



5 ^s „ 2 



16 ?8 „ 1 

 12 c?s „ 1 

 = 22 ? 8 and 18 <? s. 



A statement by Prof. Perez in his memoir, " Des effets du Para- 

 sitisme des Stylops sur les Apiaires du genre Andrena," referring to 

 the appearance of stylopized bees with no apparent Sfj/Iops, that the 

 parasite may be hidden in the abdomen, or may be present in the larval 

 stage of the bee, led me to examine two apparently stylopized speci- 

 mens of atriceps ; in both of these was a ? Stylops deeply embedded 

 in the viscera. 



Naturally we should expect the larva of the Stylops to destroy 

 the reproductive germ cells in the maggot of the bee ; this would 

 account for the curious changes in stylopized bees (the ^ assuming 

 the appearance of the $ , and vice versa), and yet Mr. Perkins finds 

 ova and spermatozoa in course of development in the infected speci- 

 mens. What, then, in this case, can the changes produced by stylo- 

 pization be due to ? 



