56 NATURAL SCIENCE. "t^^"- 



were liardly affected by the presence of the parasites, and that the 

 males certainly, and the females probably, were still capable of 

 reproduction. These results are extremely surprising, being in direct 

 contradiction to those obtained by Shuckard, Westwood, and Perez. 

 The last-named of these, a few years ago, gave a very full account of 

 stylopised bees (" Actes Linn. Soc, Bordeaux," vol. xl., p. 21). Mr. 

 F. V. Theobald, however, confirms, to a great extent, the work of 

 these older observers (" Entom. Monthly Mag." [2] , vol. iii., p. 40), and 

 makes it likely that the specimens examined by Mr. Perkins were of 

 a very exceptional nature. The Stylops, lying above the viscera, 

 obtains its nourishment by osmosis through the abnormally thin walls 

 of the alimentary canal, which, being forced down on the reproduc- 

 tive organs, renders them abortive. They do not, as a rule, contain 

 ripe ova or spermatozoa. Indeed, Mr. Perkins admits that he could 

 not find the former in any stylopised female. 



The habits of another class of parasites are described by Herr C. 

 Verhoeff (" Zool. Anzeiger," vol. xv., p. 41). These are bees of the 

 genus Stelis which have long been known to lay their eggs in the 

 nests of other bees (Osmia). Former observers had noticed the eggs 

 both of the parasite and of the host in the food-mass in the cell, and 

 at a later period had found only the larva of the Stelis. Hence it 

 had been inferred that the Osmia grub died of starvation. It seems, 

 however, that its death is really due to violence. The Stelis lays her 

 egg before the Osmia, and at the further end of the food-mass, whilst 

 the Osmia lays her egg on the surface of the food-mass. Hence the 

 two eggs are at opposite ends of the food ; and both grubs feed for a 

 time without conflict. Later, however, the Stelis, which, being older, 

 is larger and stronger than the Osmia, attacks the latter, digs its 

 mandibles into the head of its victim, kills, and devours it. The 

 time occupied by the Stelis larva in eating up the Osmia is one to 

 two tlays. 



It seems doubtful if this habit is one to which the term 

 parasitism can properly be applied. 



G. H. Carpenter. 



