THE STABLE FLY. 37 



fully extended, and nearly equals the length of the abdomen proper. 

 The eggs are passed rapidly down the ovipositor at intervals of a few 

 seconds, and were usually laid in an irregular heap. In some instances 

 the female was seen to separate the eggs by carefully passing her pro- 

 boscis between them, and then drag them away or scatter them with her 

 legs. In cases where the eggs were laid during extremis the female 

 generally died on the spot, and made no attempt to scatter them. 

 Counts were made of seven batches, the maximum being seventy-one, 

 the minimum forty-eight ; the actual counts were forty-eight, forty- 

 eight, fifty-four, fifty-seven, fifty-nine, sixty-two, seventy-one. The 

 incubation period, at an average temperature of 72 F. in the day, and 

 65 F. at night, was two to three days. 



They are especially abundant during August and September ; but 

 gradually diminish in numbers during the early part of October ; and 

 few examples are seen after a spell of cold wet weather. 



The egg is coriaceous ; white at first, but changing to creamy white. 

 Those which are laid on faeces, fully exposed to the sun, had the 

 exposed portions tinged with pinkish-brown, but this colour eventually 

 disappeared. Form, very elongate, shaped somewhat like a banana, 

 being curved on one side, and almost straight on the other ; the straight 

 side with a broad groove, which widens at the anterior end, giving it 

 a spatuloid form. Surface with faint polygonal reticulations. The 

 larva effects its escape by splitting the broad end of the groove, leaving 

 it slightly raised, and apparently intact on the opposite side. Length, 

 I mm. 



The larvae move rapidly along a smooth surface, pulling them- 

 selves along chiefly by means of a large mouth hook ; and proceed 

 practically in a straight line, moving the head rapidly, but irregularly, 

 from side to side, or up and down. There is, however, no regular 

 alternate movement of the head during progression as in muscid larvae. 

 Their progress through the burrows in their food is much more rapid 

 than on a smooth surface, and when disturbed they disappear with 

 extraordinary rapidity. The larval stage lasted, under favourable con- 

 ditions, from 14 to 21 days; but the absence of excessive moisture 

 and the admission of a little light materially retarded their develop- 

 ment, which then extended over a period of from 31 to ;8 days. The 

 larvae exposed to such conditions produced much smaller pupae, and 

 correspondingly small imagines. 



Pupation is completed in about two hours. At first the larva 

 rapidly shortens itself, chiefly by contracting the anterior segments, 

 and becomes barrel-shaped. At this period it is of a creamy-white 

 colour, and the mouth parts of the larvae are still visible through the 

 soft integument. The colour rapidly changes to bright ochreous, and 



