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emerge. With the parasites of Jassicl leaf-hoppers, emergence 

 from the puparia sometimes does not take place for a week or 

 more after capture, but these leaf-hoppers are more easily kept 

 alive in captivity than most of the Fossorial Hymenoptera. 



EFFECT OF ATTACK OF STYLOPIDAE ON THEIR 



HOSTS. 



The external and internal effects of stylopization on the hosts 

 have been studied by various hymenopterists in the case of the 

 typical genus Sfylops, but tlicy still requux much closer turther 

 examination. In 1891 I showed that males of certain species of 

 bees bearing the females of Stylops were apparently perfectly 

 capable of reproduction. I have fully verified these observa- 

 tions subsequently. Pififard has recorded the fact of a stylopized 

 male bee copulating, and I have myself since noticed similar 

 cases, but in this respect the most remarkable case observed by 

 me was that of the male of a leaf-hopper, a large species of 

 Tcttigoiiia bearing two great male puparia and two mature 

 female parasites, which was in copula with a female carrying 

 three or four parasites. Female bees of the genus Halictus 

 infested with Stylops hibernate like healthy individuals. On the 

 other hand, Theobald examining other species of Andrena came 

 to a conclusion almost opposite to my own, which may have 

 been due to the fact that the species investigated by us were 

 different. I suspect however that it was largely due to two 

 causes: (i) that he chiefly examined bees containing, or that 

 had contained, male Stylops, the efifect of which is much more 

 severe on the host than is the female parasite; (2) he examined 

 material in alcohol, and it is quite possible that^ in the process 

 of pickling, the contents of the vesiculac scininalcs were lost, as 

 I have shown this may happen on contact with water, or possi- 

 bly by the pressure of other parts on contraction in the alcohol. 

 All my specimens were freshly caug'ht ones, dissected under 

 anaesthetics, and only after the whole genital system had been 

 removed entire, glands, ducts and armature, were the bees 

 placed in alcohol for the examination of other organs. It is 

 obviously perfectly impossible that, in the species to which my 

 paper refers, the germ cells were destroyed in the larva of the 

 bee as Theobald says we should expect to be the case. 



In the case of stylopized leaf-hoppers, I should judge that the 

 efifects are a good deal the same as in stylopized bees, from such 

 observations as we were able to make on the former, (i) The 



