150 HYMENOPTERA. 



to feed on the Vespa-larvse, and Mr. Stone says that Anthomyia 

 incana is also parasitic in Wasps' nests, while two species 

 of Ichneumons, one of which is Anomalon vesparum, also in- 

 fest the larvae. No parasites have been as yet detected in this 

 country. 



The Hornet, V. crabro Linn., has, according to Mr. Angus, 

 become domesticated about New York. This and the smaller 

 wasps are sometimes injurious b}' eating into ripe fruit, but the 

 injury is more than counterblanced by the number of flies and 

 other insects they feed their young with. 



Indeed, as Saussure states, the species of Vespa are more 

 omnivorous in their tastes than an}' other wasps. They live by 

 rapine and pillage, and have obtained a worse repute than other 

 insects more injurious. In spring and early summer they feed on 

 the sweets of flowers ; but later in the season attack strawber- 

 ries, plums, grapes, and other fruits, and often enter houses and 

 there help themselves to the dishes on the table. They will eat 

 ra\^ meat, and then aid the butcher by devouring the flies that 

 lay their eggs on his meats. They will sometimes destroy Honey- 

 bees, attacking them on their return from the fields laden with 

 pollen ; they throw themselves upon their luckless victims, and 

 tear the abdomen from the rest of the body, and suck their 

 blood, devouring only the abdomen. They fall upon flies and 

 butterflies, and, biting otf their wings, feet, and head, devoui^ 

 the trunk. In attacking insects they use only their powerful 

 jaws, and not the sting, differing in this respect from the 

 fossorial wasps. 



Saussure states that though wasps do not generally lay up 

 food, yet at certain periods they do fill the cells with honey. 



The females feed their young with food chewed up and re- 

 duced to a pulp. Saussure questions whether the larvse of one 

 sex are not fed on animal and the other on vegetable food, 

 since Huber had shown "what a great influence the kind of 

 food exerts on the sex of Bees." But it is now known that the 

 sexes of some, and probably all insects are determined before 

 the larvge is hatched. I have seen the rudiments of the ovi- 

 positor in the half-grown larvae of the Humble-bee, and it is 

 most probable that those rudiments began to develop during 

 embryonic life. It is far more probable that the sexual difier- 

 ences are determined at the time of conception. 



