SYRPHIDAE OF MAINE. 217 



In Europe the larvae of Me^odon equestris (55, p. 556) and 

 Eumerus strigatus (55, p. 615) are pests of flowers such as 

 Narcissus and Amaryllis, and of the onion among vegetables. 

 The larvae burrow into, and promote the decay of, the bulbs of 

 these plants ; in certain instances having destroyed thousands 

 of plants. They have been introduced into North America and 

 are transferred from place to place in infested bulbs, and there 

 is reason to fear that their range will continue to be extended 

 and that they may become serious pests in this country. 



'On July 25, 1916, a number of the adults of each of these 

 two species was taken about blossoms in a nursery at Bar Har- 

 bor. No damage by the larvse had been recognized by the 

 nurserymen, but the number of adults present indicates that 

 the species are established in the State or are quite likely to 

 become so. 



2. As Transitory Animal Parasites. The fourth important 

 way in which larvse of Flower-flies affect us is by their occa- 

 sional occurrence in the living human or animal body and the 

 accompanying disturbances or destruction of tissues. Myiasis 

 is known to be produced by Syrphidae in four ways : First, by 

 their presence in the alimentary canal (intestinal or gastric 

 myiasis) ; secondly, by their introduction to the nasal cavities 

 (nasal myiasis) ; thirdly, by their introduction to the auditory 

 cavities (auricular myiasis) ; and fourthly, by their introduction 

 into the vagina (vaginal myiasis). 



The first of these is the more common. Probably it not infre- 

 quently occurs and is not recorded. On the other hand, many 

 reported cases of larvse having been passed from the bowel are 

 doubtless erroneous due to the stools having become infected 

 after passage. Hall and Muir, 1913, (16) have summarized 

 the published data relative to myiasis due to Syrphidae and 

 described an additional case. It appears that there are certain 

 authentic cases on record where such larvae have been passed 

 alive, sometimes as many as twenty or thirty at a time. The 

 presence of the larvae in the intestine caused some of the fol- 

 lowing symptoms : Intestinal pains, vertigo, nausea, vomiting, 

 constipation, headache, nervousness, weakness and emaciation. 



The species known to be concerned in such infestation are 

 Eristalis tenax (2, 46, 51, 29), Eristalis dimidiatus (46), Eris- 

 talis arbustorum (56) and possibly Helophilus (Musca) pen- 



