366 MEDICAL ENTOMOLOGY 



fly emerges from the pupa. From a number of observations made on 

 flies bred and mated in the laboratory he gives the following data 

 regarding the number of eggs laid by a single female : 



Length of time 



n Number of depositions Total number of 



fly was kept 



Days made 6ggS 



50 7 168 



34 9 182 



60 20 438 



72 13 435 



65 20 632 



70 11 318 



64 15 446 



In addition to the eggs which were laid a number of ripe and unripe 

 ones were found in the females after death. For instance, the fly 

 which laid 632 eggs contained ninety ripe eggs and ninety-eight 

 partially formed, so that this fly was capable of laying 820 eggs, which 

 number Mitzmain considers to be the maximum a female is capable of 

 producing. 



The egg (Plate XLVI, fig. 4) is creamy white, elongate, curved on one 

 border and almost straight on the other. The straight border has a deep 

 furrow similar to that seen in the eggs of other muscids. The larva 

 hatches in about twelve hours, and becomes mature in from seven to 

 twenty-one days, the length of the period depending on the season of the 

 year and the food supply. 



The mature larva measures from 11 to 12 mm., and is of a dull 

 white to creamy white colour ; the posterior stigmata are black and 

 almost circular. The anterior pair (Plate XLVI, fig. 6) are yellowish, and 

 have five papillae. The feeding habits of the larvae are extremely 

 characteristic ; the anterior end is rapidly protracted and retracted, 

 and the larva looks as if it were licking off the organic matter from 

 the particles of sand ; once this manoeuvre is seen, these larvae will be 

 readily detected by it. When about to pupate they leave the moist sand 

 or the dung and crawl to drier parts. The piiparlum is of a dark brown 

 colour and measures about 5 to 5'5 mm. The pupal stage usually lasts 

 about four days in the tropics, though according to Newstead it may 

 be as long as thirteen in cool climates. 



The alimentary tract of the larva of Stomoxys calcitruns is depicted 

 in fig. 2, Plate L. 



