THE FLIES THAT CAUSE MYIASIS IN MAX 13 



painful, difficult, or temporarily impossible without the aid of a cathe- 

 ter. In men it may be accompanied by painful erections followed by 

 ejaculations which may expel some of die larvae. The number of lar- 

 vae infesting a person is often small, especially in males; in some 

 female patients the number of parasites has exceeded 50. 



F iinn in canicvlaris is the species most frequently involved, but 

 Musca domestiea is also an occasional etiological agent: others that 

 have been recorded are Fanrda scalaris and Teiehomyza fusca. The 

 F'lnnia larvae were mistaken by some earlier writers for isopod 

 crustaceans. 



FURUNCULAR DERMAL OR SUBDERMAL MYIASIS 



Furuncular dermal or subdermal myiasis is caused by specific 

 myiasis-producing flies which enter either the unbroken skin, tiny 

 perforations made in the skin, or the openings of hair follicles. The 

 developing larva forms a boillike tumor, or furuncle, which opens 

 externally to permit the larva to breathe. The furuncle may be very 

 painful when the larva is feeding and may subsequently become in- 

 fected with bacteria, or by the invasion of screwworms and other pro- 

 ducers of traumatic myiasis. Death of the larva within the tumor 

 often has serious effects as a result of bacterial contamination. The 

 larva is capable of completing its development within the furuncle, 

 after which it will emerge, drop to the ground, and pupate. After 

 emergence of the larva healing is rapid if no complications are present. 



Several species of flies, of different taxonomic groups, may cause 

 this type of myiasis. Those commonly involved are Dermatobia 

 hominiS) Wohlfahrtia vigil. W. opaca, Oordylobia anthropophaga, and 

 Stasisia rodlumd. Callitroga americana will produce a similar tumor, 

 when the invasion is made by a very small number of larvae and 

 through a very small puncture in the skin, or possibly through the 

 unbroken skin: and the final stage of Hypoderma will likewise pro- 

 duce a furuncular swelling. 



CREEPING DERMAL OR SUBDERMAL MYIASIS 



It has long been known that two genera of Diptera. Gasterophil/us 

 and Hypoderma, may be involved in a condition called variously as 

 creeping disease, creeping eruption, larva migrans, and by other medi- 

 cal and vernacular names. Since the geographical distribution of the 

 diease is more extensive than that of the flies supposed to cause it, 

 other etiological agents were sought. It is now 'known that cases in 

 Florida. Africa, and other tropical and subtropical regions are due 

 to nematodes and not to fly larvae. Kirby-Smith. Dove, and White 

 have di>cussed the situation in Florida in relation particularly to 

 nematodes but also to insects. In general, multiple infestations in 

 the outer layers of skin, contracted in areas extralimital for Gastero- 

 ph'/his. are probably nematode and not insect infections. 



Human myiases involving GasteropMlus and Hypoderma differ 

 greatly from each other. In GasteropMlus the tunnels appear as 

 narrow raised lines which progress at one end and fade out at the 

 other: they extend through the upper layers of skin in a serpentine 

 fashion, often crisscrossing each other. The boring of the larva often 

 occasions severe itching but no pain. Hypo<h rma galleries, on the 



