208 BRITISH BEES. 



the birds, thrives at the expense of the young of the 

 sitos by consuming its food, and thus starving it. These 

 parasites consist of many of the species of Nomada, 

 very pretty and gay insects, but in every case totally 

 unlike the bee whose nest they usurp. Several of the 

 species of these Nomada are not limited to any particu- 

 lar species of Andrena, but infest several indifferently, 

 whereas others have no wider range in their spoliation 

 than one single species, to which they always confine 

 themselves. In my observations under the genus No- 

 mada I shall notify those which they assail amongst the 

 Andrence, as well as the other genera which they also 

 infest. 



The others which attack them are more properly po- 

 sitive enemies than parasites, for they prey upon the 

 bees themselves, or, as in the case of the remarkable 

 genus Stylops, render the bee abortive by consuming 

 its viscera and ovaries. I have spoken of these insects 

 in the chapter upon parasites, to which I must refer, 

 but I may here add that the female is apterous, and 

 never quits the body of the bee. Much mystery at- 

 taches to their history in which their impregnation is 

 involved, for the male, immediately upon undergoing its 

 change into the imago, escapes through the dorsal plates 

 of the abdomen of the bee wherein it was bred and 

 takes flight. In localities where they occur they may 

 be usually taken on the wing in the month of May. 

 The female would seem to be viviparous, and produces 

 extraordinary multitudes at one birth, extending to hun- 

 dreds. Being born as Iarva3 within the body of the 

 bee they seek to escape from their confinement, and find 

 the opportunity in the suture which separates the rneso- 

 thorax from the metathorax. Their extreme minuteness 



