ms.] no 



males of this bee may have not only the clypeus but an additional spot 

 on each side of the face adjoining this, yellow. 



The most important external change produced by Siylops in its host 

 is, without doubt, the degeneration of the pollinigerous apparatus of 

 the hind legs. This, of course, affects the female bee only, and it is 

 questionable whether — at any rate in most of the species subject to 

 stylopization — an}^ parasitized individual has these perfect. In fifty 

 examples of A. irimmerana the seopae exhibit much difference in the 

 deo-ree of their degenemtion, and even when at first sight they appear 

 practically normal in size, it will be found on closer examination that 

 the hairs which sprmg from the lower side of the tibiae do not exhibit 

 that curvature upwards round its outer surface in so perfect a degree as 

 in a healthy bee. This degeneration is no doubt strictly correlated with 

 injury done to the ovaries and is never seen in non-stylopized examples ; 

 so also is the assumption of white or yellow facial markings in some 

 females of A. lahialis, coitana^ chrysosceleSy and probabW of tarsata 

 {analis^. Whether a diminution or entire loss of such markings in the 

 males of yellow-faced species is also coiTelated with injury to the 

 genitalia appears to me much more doubtful. 



Every one who has studied bees must have noticed that different 

 individuals are very differently a"ffected by Stylops, but it is much less 

 easy to demonstrate, largely indeed for this very reason^ that different 

 species react differently to the attacks of the pai-asite in important 

 respects (<?. g. the deterioration of the pollinigerous organs). This, 

 however, appears to be the case, and cases will be given when the species- 

 are considered separately. E. Saunders speaks of the "assimilation of the 

 sexes " caused by stjdopization. This tendency to some simikrity of 

 appeai-ance seems to me to be due to the following causes ; Inflation 

 of the abdomen, caused no doubt by pressure from the parasites, affects- 

 both sexes very commonly, and this causes the usually much more slender 

 males to have more the appearance of the other sex* Both sexes are 

 often similarly influenced as to the condition of the abdominal pubes- 

 cence, this being either decreased or increased or changed in appearance 

 in (S and $ alike. When the 6 and $ are under normal circumstances 

 unlike in this character, their general appearance when similarly altered 

 by stylopization naturally becomes more close. The notable decrease iiii 

 size of head of S and $ sometimes causes some resemblance between the 

 sexes in this respect. 



In extreme cases of deterioration of the pollinigerous organs the 

 hind legs of the female, by the diminution of the seopae and their more 

 slender tibiae, make- some ajiproach to the 6 condition. 



