DIPTERA. 



'61 



BLACK AND WHITE BEE-FLY, WITH PUPA-SKIN 

 PROTRUDING FROM COCOON OF BEE. 



for the cells of solitary bees wherein to deposit their eggs. The left-hand figure 

 shows the cocoon of one of these bees, with the pupa-case, from which the fly on 

 the right has just emerged, protruding 

 from it. For the last family of this section 

 (Stratiomyidce) the common Stratiomys 

 chamceleon may be taken as the type. 

 This is a rather large insect, with a short 

 broad abdomen, variegated at the sides 

 with pale spots ; the sides of the face and 

 the posterior part of the upper surface of 

 the thorax being also yellow. The antennae 

 are longish, and the hinder part of the 

 thorax is armed with a pair of spines. 

 The females, which may be seen on the 

 wing in the neighbourhood of marshes, 



ponds, and ditches, lay their eggs on the leaves of water-plants, and the larvae spend 

 their time wriggling about in a helpless way. In these larvae the body consists of 

 twelve segments, is somewhat depressed, pointed at each end though more so 

 towards the tail than the head and covered with a tough blackish brown skin. 

 The head is small and pointed, and the retractile tail-segments are furnished at the 

 tip with a breathing-orifice surrounded by a circlet of barbed hairs. By means 

 of these the larva is enabled to suspend itself from the surface 

 of the water, hanging vertically downwards with the orifice 

 just above the water's level , and is also able by the folding 

 in of the hairs to take a bubble of air below the surface when 

 it sinks to the bottom. The larvae feed on such particles of 

 matter as they find in the water ; and when ready to pass into 

 the pupal stage creep to the land, and take refuge beneath a 

 stone, or in some other place of safety. The development of 

 the pupa and perfect insect takes place only in the front part of the larval skin. 

 A curious choice of habitat for her young on the part of some flies belonging to 

 this family has been recorded from Wyoming. These larvae were found in a cup- 

 shaped depression at the top of a cone about twenty inches high situated a few 

 feet from a large sulphur mound, under which the boiling water could be heard. 

 Through small apertures in the bottom the hot water rose and filled the cup. 

 It was in this that the larvae were found; and it is estimated that the tem- 

 perature of the water was only twenty or thirty degrees below boiling point. 



FEMALE OF Stratiomys 

 chamceleon. 



CIRCULAR-SEAMED FLIES, Suborder Cyclorrhapha. 



This suborder, which is characterised by the circumstance that the pupa escapes 

 from the larval skin through a circular aperture formed by the pushing off of the 

 head-end, contains the majority of ordinary flies. It is divisible into two sections, 

 the first of which includes those that present the normal method of development, 

 the young being hatched from eggs laid by the mother, although very rarely the 

 eggs hatch immediately before being laid. The second embraces those in which 



