526 



FLY MAGGOTS AND MYIASIS 



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

 (Fig. 253) diflfer 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 fa>ces 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 larva' of the chee.sefly, Piophila casei, popularly called 



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

 larvae often occur in al)undance in old 

 '^^^^ cheese, and also in ham, bacon and other 

 '^^^f^ foods. It is thought by some people that 

 Ihcir 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 larva? 

 have a single median one. Probably in 

 Fig. 254. Cheesp-skippcr j^y^^y cases the cheese-skippers pass 



and adult, Piopnila casei. ' i i • • i i • 



X 3. (After Graham- through the mtcstme Without domg much 

 s.i.itii from Riley and dj^n^jre h\\{ thcv sometimcs attack the 



Jolianusen.) " • i i i- 



mucous membranes, causmg 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, Sarcuphaga fitscicauda. 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 Ix- of interest only as ab- 

 normal occurrences. 



The powerful resistance of fly maggots to substances which 

 would (juickly destroy other animals makes it possible for many 

 species to pass lhr(nigh the stomach .safely if accidentally swal- 

 lowed either as eggs or young worms. .\s saicl before experi- 

 ments show that the larva- of the fleshfly, Wohlfartia magnifica, 

 can survive twcj hours in ','.') pci' cent ulcohol, und ten minutes in 



