THE ENTOMOLOGIST. 16 



As a contribution to thivS subject I beg to put on record an 

 incident which my brotliev and I witnessed during an after- 

 noon's ramble at the latter end of August last. We were 

 "prospecting" in a favourite nook of ours in Epping Forest, 

 near the village of Woodford, when we chanced upon an 

 astonishing sight: a patch of fern and broom, about four 

 yards square, was literally blackened by a swarm of a little 

 fly. Sepsis cynipsea, L. ; every frond and twig seemed alive 

 with the myriads of insects, slowly moving about and gently 

 fanning their beautiful, spotted, iridescent wings with a 

 steady and simultaneous motion. Some idea of their pro- 

 digious numbers may be formed when I mention that two or 

 three sweeps of a butterfly-net secured a mass of flies which 

 weighed more than half a pound ! We noticed that the mass 

 exhaled a rather strong, and by no means an unpleasant, 

 odour of "lemon-thyme." The swarm consisted of males 

 and females; but a long examination of the spot failed to 

 throw any light on the cause of this assembly. The larva?, 

 Mr. Walker informs me (1 am indebted to him for the name 

 of the insect), feed on decaying matter, but we could find no 

 difference in this respect in the small patch of herbage 

 covered with the insects, or the ground beneath them, com- 

 pared with the surrounding open forest glade. Mr. Walker 

 once found a large cluster on a statue in Highgate Cemetery. 

 I shall be glad if this notice leads to the publication ot 

 similar facts, for a rational explanation of this class of 

 phenomena, based on observation, would certainly be wel- 

 comed by all lovers of Nature. — Wm. Cole ; The Common, 

 Stoke Newington, N. 



Certain Insects emerge from the Pupa hij Hydraulic 

 Pressure. — Being only a beginner and having seen nothing 

 in any work I have read on the emergence of insects from the 

 pupa, but that they "wriggle out," 1 was surprised and 

 delighted when I saw the wonderful power at their command 

 to effect their deliverance. Ou the 14th of July last, as I sat 

 watching some Bembeciformis dry themselves after their birth 

 on the stem of an old willow, 1 took in my fingers a pupa that 

 had just come to the mouth of its tunnel, and holding it 

 between my eye and the light, being in a gloomy part of a 

 wood at the time, 1 saw that the anal segment of the case was 

 empty, and the enclosed insect emitting several drops of fluid 



