44 LIFE-HISTORY 



locomotion, and also in tearing up the food which is absorbed in 

 a semi-fluid form, the solid portions, such as small pieces of 

 straw, etc., not being taken into the mouth. At the sides of the 

 second segment is seen a pair of golden fan-shaped organs, each 

 having six to eight lobes or rays. These are the anterior 

 spiracles, through which air is taken into the respiratory tubes 

 of the larva." 



" A second pair of eye-like spiracles, the posterior spiracles, 

 is found in the middle of the obliquely blunt posterior end of 

 the larva. Each of these consists of a black chitinous ring 

 enclosing three sinuous slits through which air passes into small 

 chambers at the ends of the pair of thick longitudinal respiratory 

 tubes. On the ventral surface of the larva at the anterior edge 

 of each of the sixth to twelfth body segments is a crescentic 

 shaped pad covered with short recurved spines. These locomotory 

 pads take the place of legs and are used by the larva in con- 

 junction with the mouth-hook in travelling backwards and 

 forwards. The anus is situated between two prominent lobes on 

 the ventral side of the terminal segment. The larva is covered 

 by a thin cuticular integument through which the internal organs 

 may be observed in younger larvje. As the larva becomes 

 mature, the growth of the fat tissues gives it a creamy appear- 

 ance and the internal organs are obscured " (Hewitt, 191 2, p. 23). 



Newstead (p. 14), from his experience of the larva in Liver- 

 pool, says " it is essentially a vegetable feeder ; animal matter is 

 eaten only, so far as one has been able to gather, when in the 

 form of human faeces. It was never found feeding on the 

 carcases of dead cats and dogs, or on bird and fish remains." 

 Hewitt (1908, p. 499) however successfully reared larvae in 

 " horse-manure, cow-dung, fowl-dung, both as isolated faeces and 

 in ashes containing or contaminated with excrement obtained 

 from ash-pits attached to privy-middens, and such as is some- 

 times tipped on public tips. I found that horse-manure is 

 preferred by the female flies for oviposition to all other substances, 

 and that it is in this that the great majority of larvii^ are reared 

 in nature; manure heaps in stable yards sometimes swarm with 

 the larvae of M. douiestica. It was also found that the larvae feed 

 on paper and textile fabrics, such as woollen and cotton garments 



