82 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



place. The period from egg deposition to emergence of the adult is 

 22 to 24 days. 



Rats seem to be the normal host and probably form the reservoir of 

 the parasite in nature. Heavy infestations in that animal may be 

 fatal. Dogs are often severely parasitized, sometimes so much so that 

 death will result. Man is a common host. The young larva usually 

 enters the skin of man without making itself felt. As it develops 

 a red papule forms which ultimately develops into a boil, open at the 

 apex and disclosing the larva which appears like a core. At this time 

 the pain may be so great as to interfere with sleep. No great quantity 

 of pus is formed, but much serous fluid may exude at times when the 

 larva is feeding. The skin is indurated, and the area around the 

 tumor is tender to pressure ; the cavity is out of proportion to the size 

 of the larva. After the removal of the larva the symptoms disappear 

 and healing is rapid. In the case of an infection, however, particu- 

 larly when the larva dies within the cavity, the tumor may become a 

 purulent abscess. 



The larva may be expelled by gentle pressure, but that is often 

 painful. The application of a thin film of liquid paraffin will force 

 the larva to back out in an attempt to get oxygen; if the film is 

 gradually thickened, the larva will entangle its posterior end in the 

 paraffin, so that removal may be made much easier. Prophylactic 

 measures are based on the principles of elementary hygiene. Wash- 

 ing and ironing bedding and underclothes exposed to the air will 

 destroy eggs and young larvae that are highly sensitive to heat, Rats 

 should be exterminated, and domestic animals kept free from the pest. 

 Latrines should be kept flyproof. and sand kept in outdoor latrines 

 should be sterilized. It is possible for both man and animals to develop 

 a certain degree of immunity. 



Literature. — Two important works that treat the biology and patho- 

 genesis at length, with descriptions of the various stages of the fly, 

 are by Roubaud (126) , and Blacklock and Thompson (19) ; for a more 

 recent study of the larva, see Bertram (14) . 



The Genus STASISIA Surcouf 



This is a genus of flies similar in appearance to Cordylobia. The 

 haustellum is stout; the palpi flattened and widened, more so in the 

 female than in the male; and the arista is thinly plumose on about 

 the basal three-fourths, the hairs above being longer than those below. 

 The front is almost parallel-sided in both sexes and almost one-fourth 

 the width of the head. Proclinate fronto-orbital, ocellar, and outer 

 vertical bristles are lacking in both sexes. There are three presutural 

 acrosticals and two sternopleurals. Vein r 3+4 is ciliated about halfway 

 to cross vein r-m; there is no costal spine. 



There is but one known species. 



STASISIA RODHAINI (Gedoelst) 



The Larva of Lund 



Synonym. — Cordylobia rodhahii Gedoelst. 



Recognition Characters. — Adult : This is a yellowish fly with the abdomen 

 chiefly shining black or brown. Larva : The mature larva (fig. 39, B) is a robust 

 grub about 17-33 mm. in length by 8 mm. in maximum width. The body is 

 strewn, dorsally and ventrally, with sparse but large spines ; those on the last 

 two segments, however, are few and very small. The last body segment is retracted 



