534 Mr. G. A. K. Marshall on 



box ou purpose to include the hirge XyJocopa bee whicli it 

 mimics so admirably; but though usually they are common 

 enougii I have not seen a single example for the last three 

 weeks. The fly completely deceived me when on the 

 wing, but I happened to notice it settle on the trunk of a 

 tree, and it struck me there was something curious about 

 the way it alighted for a XyJocopa. It is the only 

 example I have seen. 



Salisbury, April, 25, 1890. — I have already got a couple 

 of the Xi/locopas for you, and I have seen another 

 specimen of the Zaphria that mimics them, but unfortun- 

 ately failed to catch it. 



/I St/rphid Fly Mimicking a Wasp (Represented on 

 Plate XXIII). 



Hymexopteha. Dipteka. 



Polistcs marginalis (fig. 40). Ccvia ganibiaiia (lig. 41). 



This is an excellent and typical case of Batesian 

 mimicry. The wasp is a very common species, building 

 a small hanging nest on bushes or grass-stems. Like most 

 of its congeners it is a somewhat sluggish insect, and in- 

 stead of flying away when approached, adopts a bold and 

 defiant attitude, stinging sharply when disturbed. It 

 visits flowers freely, and may there be seen in company 

 with the (Jcria, whicii resembles it so closely (especially 

 on the wing) that I have been deceived by it over and 

 over asfain. 



y. Bcc-lilcc Group (Represented on Plate XXIII), 



llyjlENOPTEKA. DirXEItA. 



Apidx. Syrphkhv. Asilidie. 



Megacliilc ajiironnis Euiiioins, sp. nov. ? l.axciiecera mollis 



(fij. 37). (tig. 38). (Hg. 39). 



The resemblance of the two flies to the Mcgachile 

 is very marked in the field, especially in the case of the 

 Laxcncccra ; although the plate does not do justice to the 

 Eumerus. I have on several occasions seen all three 

 species flying together in the vicinity of flowers. 



