1907.] 229 



NOTE ON THE COUPLING OE EMl'IS BORKALFS. 

 BY MI LB URN IIOWLETT. 



During a recent visit to the Highlands I noticed how frequently 

 the female of Empis borealis was feeding during (he act of co[)ula- 

 tion. This peculiarity of Euipids has often been commented on, but 

 without, as far as I know, anything more than a casual connection 

 between the two acts being inferred. Bearing in mind Professor 

 Poulton's recent work on the diet of Empids, I caught during one 

 afternoon five pairs of E. borealis in cop.^ and found that all the females, 

 without exception, were engaged on a meal, while of a dozen females 

 caught alone none had prey. Sain put a stop to further observations 

 that day, but on the next opportunity (June 11th) I revisited the 

 same spot, as it seemed to be a favourite trystiug-place, meaning to 

 try to see whether the male habitually took advantage of the moment 

 when the female, engaged with prey, could not conveniently repel his 

 advances. I took two pairs in cop., and, as before, both the females 

 had i)rey ; a flying lone male also had prey, but did not seem to be 

 eating it. The sun having made its appearance, some of the flies 

 could now be seen dancing about the lower branches of some firs by 

 the side of a little burn, some eight or nine feet from the ground ; 

 soon another, carrying prey, joined them, and flew up and down below 

 the dancers in a provocative manner. After a few moments one of 

 these latter responded, and, after a second's struggle in mid-air while 

 they coupled, the pair flew slowly off and settled on some low heather 

 bushes near by, the female sucking the prey. I had taken it for 

 granted that the dancers were males, and the solitary prey-bearing 

 visitor a female who had been pounced on as she passed, but ou 

 returning to the firs it was soon apparent that the dancers were all 

 females, for as the sun passed behind a cloud they settled down ou 

 the ends of the fir-twigs, where they could be inspected at leisure, and 

 it was, besides, not diflicult to distinguish the sexes even when ou 

 the wing. When next the sun came out and the dance began again, 

 another prey-bearing visitor came up, and exactly the same programme 

 was goue through as on the previous occasion. A third visitor was 

 caught just as copulation was apparently about to take place, and 

 this proved to be a male carrying a delicate. Neuropteron {Ghloro- 

 pcrla, sp.) not only alive and unwounded, but iu strikingly good 

 condition, quite fit for a cabinet specimen. 



Thus it appeared that the male brought up a choice specimen, 

 which he transferred to the female during their brief aerial struggle 



