THE STRAIGHT-SEAMED FLIES 



3023 



BLACK AND WHITE BEE FLY, WITH PUPA 

 SKIN PROTRUDING FROM COCOON OF BEE. 



proboscis, which is thrust into blossoms while the insect (No. 8 on p. 3028) stays 

 poised in mid-air, like a hawk moth when similarly occupied. The black and white 

 bee fly (Anthrax semiatra) is mostly of a black tint, and clothed with hair of the 

 same color; but the hairs on the front part of the thorax and abdomen take a yel- 

 lowish tinge, the wings, as shown in the illustration, being black in the basal half 

 but clear elsewhere. These insects may be seen on the wing in dry, sunny spots, 

 stopping from time to time to suck a flower, or rest upon a stone, and seeking 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 

 (jStratiomyidcc) 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 neighborhood 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 

 toward 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 downward 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 temperature of the water was only twenty or thirty degrees below boiling 

 point. 



FEMALE OF Stratiomys 

 chamceleon. 



