526 FLY MAGGOTS AND MYIASIS 



manner of flight as its close relative, F. canicularis. The larvae 

 (Fig. 253) differ from those of the latter species in the form and 

 arrangement of spines. Several cases are on record in which 

 Fannia larvae were passed in the faeces intermittently for a num- 

 ber of years, often accompanied by a chronic disorder of the 

 intestine. It is probable in these cases that repeated reinfections 

 occur, though it may be conceived that the complete life history 

 of the fly could be passed within the intestine of the host. The 

 probability of this seems rather remote. 



Other Species. Another common cause of intestinal myiasis 

 is the larvae of the cheesefly, Piophila casei, popularly called 

 " cheese-skippers " (Fig. 254). These 

 larvae often occur in abundance in old 

 cheese, and also in ham, bacon and other 

 foods. It is thought by some people that 

 their presence in cheese is an indication 

 of particularly good cheese! These mag- 

 gots resemble diminutive housefly larvae, 

 but have two mouth hooks like the blow- 

 fly maggots, whereas the housefly larvae 

 have a single median one. Probably in 

 FIG 254. Cheese-skipper man y cases the cheese-skippers pass 



and adult, Piophila casei. .'.',, , . 



x 3. (After Graham- through the intestine without doing much 

 Smith from Riley and damage, but they sometimes attack the 



Johannsen.) 



mucous membranes, causing bleeding sores 



which may become infected and ultimately lead to ulceration. 

 Severe pain in the abdomen, headache and vertigo have been 

 known to be caused by these larvae in the intestine. 



There is one case on record of the infection of a Chinaman 

 with the fleshfly, Sarcophaga fuscicauda. He passed about 50 

 larvae in each stool for eight days. Occasional infection of the 

 intestine with maggots of other species of flies has been recorded, 

 but the instances are so rare as to be of interest only as ab- 

 normal occurrences. 



The powerful resistance of fly maggots to substances which 

 would quickly destroy other animals makes it possible for many 

 species to pass through the stomach safely if accidentally swal- 

 lowed either as eggs or young worms. As said before experi- 

 ments show that the larvae of the fleshfly, Wohlfartia magnified, 

 can survive two hours in 95 per cent alcohol, and ten minutes in 



