188 SANITARY ENTOMOLOGY 



of cattle, in some cases causing the death of many calves, especially when 

 the cutaneous tumors become infested with larvas of Chrysomya. 



The life history and habits of the species have not been fully eluci- 

 dated, although a number of important contributions have been made. 

 It is generally concluded that the infestation of man is brought about in 

 the following indirect but very interesting manner : The eggs of the fly 

 are deposited on the bodies of certain bloodsucking insects, especially the 

 mosquito known as Psorophora lutzi Theobald (Janthmosoma), or 

 attached to leaves frequented by these insects whence they adhere 

 to them. The eggs are attached vertically on the under side of the 

 abdomen or the legs. The embryos appear to remain dormant though 

 fully developed within the egg and when the bloodsucking dipteron 

 finds a host, the heat of the animal or the blood taken up stimulates the 

 larvae to break from the shell and penetrate the skin of the host. Dermal 

 tumors are formed by the larvae, a well-marked hole opening to the outside 

 as in the case of the ox warble. When the grubs become full grown they 

 leave the host, drop to the ground and transform to adults. The period 

 in the host ranges from two to six months. During this time there is 

 more or less inflammation and sometimes acute pain. This form is widely 

 distributed through tropical America. Lieut. L. H. Dunn has recorded 

 cases of apparent transmission of the eggs by ticks. 



In South America Dr. J. C. Nielson has reported the occurrence of the 

 Anthomyid flies {Mydaea anoTnala and M. torquens) as producing'subcu- 

 taneous tumors in various birds in parts of Argentina, and Dr. C. H. T. 

 Townsend records M. spermophilae as parasitic on nestlings in Jamaica. 



Europe. — Several cases of dermal myiasis have been reported, espe- 

 cially from Russia. These are attributed to infestations of larvae of 

 Hypoderma and Gastrophilus. 



The infestation of reindeer in Lapland and farther south in Norway 

 by larvEB of the Oestrid fly, Oedemagena tarandi Linnaeus, should be 

 mentioned. The infestations are almost analogous to those in cattle 

 caused by Hypoderma. The eggs are laid on the hair during the spring 

 and later the larvs appear in the submucous tissues of the back. As 

 many as 300 have been reported as occurring in a single animal. This 

 same species no doubt infests the reindeer in Alaska and Canada. 



Africa. — In Africa the outstanding form of dermal myiasis is pro- 

 duced by the Muscid fly, Cordylohia anthropophaga Griinberg, commonly 

 spoken of as the Tumbu fly (figs. 38, 39). The larvse are known as "Ver 

 du Cayor." These develop in the skin of man and various other hosts 

 including dogs (probably the preferred host), cats, horses, and other 

 domestic and wild animals. The attack is painful but not serious, though 

 no doubt when numerous specimens are present unpleasant symptoms fol- 

 low. The life history of this form has not been entirely elucidated, but 



