1889.] 293 



Probably most of our nurserymen, who grow onions for seed, are 

 well acquainted with the larvse of assectella, their gregarious habits 

 necessarily impressing the most unobservant, though very likely they 

 only know them as " nasty white maggots," and would be much 

 surprised to hear that they had a money value amongst collectors of 

 insects. 



Monntsfield, Lewisham : 



May 16th, 1889. 



ANDRENA AND STTLOPS. 

 BY EDWARD SAUNDERS, F.L.S. 



I was at St. Leonards at Easter this year, and on the Croft, 

 Hastings, was fortunate in taking several specimens of Andrena 

 atriceps attacked by Stylops. On my return home I looked up such 

 other specimens of Stylopized Andrencs as I possessed, and I propose 

 to offer a few remarks on them. 



In my "Synopsis of British Hymenoptera'''' (Trans. Ent. Soc. 

 Lond., 1882, p. 228) I made some observations on Stylopization, 

 quoting from a letter from Prof. Perez, of Bordeaux, on the subject. 

 Since then the Professor has published, in the " Actes de la Societe 

 Linneenne de Bordeaux, 1886," a most interesting memoir, entitled, 

 " Des effets du Parasitisme des Stylops sur les Apiaires du genre 

 Andrena,''' in which he enumerates the various changes, external and 

 internal, that he has noticed as the result of the action of the parasite, 

 and it may not be uninteresting to mention here some of the chief 

 changes which he notices to have been effected in the host by the 

 presence of this curious Coleopteron. In most cases I have observed 

 the same peculiarities myself, so that I can fully corroborate the 

 remarks he makes. 



In the Stylopized form, the abdomen becomes more globose, and 

 the posterior margin of its 5th segment becomes shortened and its 

 teguments thinner ; the head narrower and smaller ; the puncturation 

 and villosity of the entire insect denser ; and, in the case of Andrence, 

 such as squamifera, in which the pubescence is depressed and scalelike 

 (of this form we have no British exponent), the pubescence tends to 

 become elongate and like the usual form ; and, as I mentioned in my 

 Synopsis, either sex, when affected by the parasite, tends to lose its 

 peculiar sexual features, and to assimilate to a common type. This is 

 strikingly observable in the reduction of the size and the alteration of 



