Effects of Castration in Insects 42 1 



formswere infested and modified by the Mermis, but Mrazek ('08) 

 has recently shown that the virgin queens of the European Lasius 

 alienus may become infested with this worm and that when this 

 occurs the insects develop abnormally^ small wings (Fig. 'jB). 

 These individuals, or mermithogynes, as Mrazek calls them, have 

 been seen by other investigators and described as brachi/pterous 

 to distinguish them from the normal macropterous individuals of 

 the species. 



After seeing Mrazek's paper I examined a small collection of 

 seven brachvpterous and as many macropterous females of La- 

 sius neoniger (a form closely related to alienus) which I had 

 taken from a single colony near Manitou, Colorado, August 9, 

 1903. Three of the short winged individuals were dissected and 

 each was found to contain a large coiled Mermis, 53 to 55 mm. long, 

 which filled out the whole abdomen, so that in the living indi- 

 viduals there could have been little leftof the reproductive organs 

 and other viscera. There is nothing unusual in these females 

 except the small size of their wings, which measure only 6 to 

 6.5 mm. in length, whereas those of normal L. neoniger females 

 measure 10 to 11 mm. These observations show that the queens 

 of our American Lasii may be affected by Mermis in exactly the 

 same manner as the queens of the related European species. 



The species of Mermis are not, however, the only known gono- 

 tomic nematodes. A much more extraordinary form is Sphaeru- 

 laris bombi, which has been known ever since the days of Reaumur 

 (1742) to produce sterility in the hibernating queens of bumble- 

 bees. According to Leuckart ('87), who has written the best 

 and apparently also the most recent account of Sphaerularia, 

 infested bees are sometimes found, "which have not a single ma- 

 ture egg in their ovaries. Structurally these organs are perfectly 

 developed and have ova in the blind ends of their ovarioles, but 

 ripe eggs are lacking. In other specimens one may find in addi- 

 tion to the young, also some ova of perfectly normal dimensions." 

 He says that he has "never seen an infested queen which had the 

 ovarioles as uniformly and richly provided with eggs as are the 

 ovaries of healthy bumble-bees at the same season. As a rule, 

 one finds only a few eggs, sometimes only a single egg." These 



