66 Ohservations on Insects affectimj the Turnip ( 'rops. 



at the base, the hinder entirely black, excepting- the tips ; the feet, 

 which are brown, have five joints each, they are terminated by 

 two little clavvS and two lobes, called pulvilli ; the fly is from 

 J an inch to 9 lines long:, ^^^^ expands from 1 inch to 13 lines. 



This is a fly which is seen from June to the end of October 

 hovering over wild and garden flowers in fine weather, and rest- 

 ing in cloudy days on trunks of trees and paling, with 'their wings 

 closed and lying upon their backs. Some idea may be formed of 

 the numbers of the larvae, and the consequent benefit derived 

 from their operations, when we state that on the 30th July, 1818, 

 which was a very hot day, these flies were in such swarms that they 

 fjuite cov^ered the fishermen's boats at sea off Broadstairs, and they 

 were equally abundant at Ramsgate and the Nore. When thus 

 congregated, insects fly in one direction, not even avoiding ob- 

 jects that lie in their course ; and in the above instance, it 

 appears, that they were bound to the hop-gardens in Kent, where 

 the crops often fail through the effects of the Aphides, as we 

 have already observed. The maggots of this species are green, 

 and I found them in July of the following year in some abund- 

 ance on the sea-cabbages, Brassica oleracea, which grow under 

 the cliffs near Dover. Many of them had been stung by a little 

 parasitic fly called Microcjaster Lineola/^^ the maggots of which 

 came out of the Scaeva larvae, and formed little elliptical silken 

 cocoons almost white. 



20. S. Ribesii, Linn, is a similar fly in form, but smaller ; the 

 head is yellowish, the nose horny- and shining; eyes coppery; 

 horns rust-colour, black above ; trunk bottle-green, scutel yellow ; 

 body black, with a large yellow or orange spot on each side of 

 the base, then follow two broad and two narrow bands; the legs 

 are bright ochraceous, the base of the thighs fuscous ; wings the 

 same as in S. Pyrastri ; length 5J- lines, expanse 11 lines. 



This fly is abundant everywhere in England in the summer, 

 especially in July : it is equally common in Scotland and Ireland, 

 where I have taken many specimens. 



21. S. balteata, Linn, is more slender in its form; the head 

 and thorax are brassy-green, the latter with two greyish lines 

 down the back ; the face is ochraceous and hoary ; horns bright 

 rust-colour, black above ; eyes as usual ; scutel ochraceous^ more 

 or less brassy at the base ; body elliptical, shining black, with two 

 bright ochraceous spots on each side of the base, and uniting 

 outside : there are also six bands of the sam^e colour, the first and 

 third being narrow ; wings as usual ; legs and under-side of body 

 entirely ochraceous; length 4 J lines, 10 in expanse. 



During July, August, and September these flies are abundant 



* Curtis's Guide Gen. 554, 1, and Brit.Ent. fok and pi. 321. 



