DIPTERA. BRACHYCERA. 361 



rising from the flowers if disturbed. The pupa of Eristalis 

 tenax, in and out of the puparium or larva skin, is figured 

 p. 5, and the reader will observe that the long tail, used 

 by the larva as a breathing tube, still remains attached 

 after its change. 



Another Fly, not occurring so abundantly, yet common 

 enough and remarkable enough to attract attention, is 

 Volucella pellucens. This insect is noteworthy both as 

 one of the Parasitic Flies and also on account of its very 

 singular appearance, which arises from the perfect trans- 

 lucency (and semi-transparency) of the basal half of the 

 large oval abdomen. 



The thorax and the hinder-half of the head are black, 

 and the effect of the clear, colourless, and apparently 

 empty fore-half of the abdomen, is heightened by the 

 colouring of the wings, which, clear at the base, have a 

 brown mark across them exactly corresponding with the 

 darkened half of the abdomen. The antennae are beau- 

 tifully feathered. Another species, V. Bombylans, is 

 hairy, and has a remarkable resemblance to the Humble 

 Bees, whose nests it enters for the. purpose of depositing 

 its eggs. 



The genus Syrphus contains some Flies similar in form 

 to the preceding, and others of smaller size with narrow 

 linear abdomens, and always marked with black and 

 yellow, or whitish bands or spots. They have a peculiar 

 mode of hovering, apparently motionless, over flowers, 

 making sudden darts forwards and from side to side. If, 

 however, the apparently motionless Fly be observed with 

 attention, it will be seen that the rapidity of motion in 

 the wings is so great as to render them almost invisible. 

 Syrphus pyrastri, a common species, is figured PI. XV., 

 fig. 4. The long pear-shaped or flask-shaped brown 



