Insecta. 277 



5: the 5 may be gnided by the smell of the food of the larva to lay its eggs 

 therein, and the more specialised in diet the larva is, the uiore narrowly would 

 the 5 sense of smell be adjusted. Definite Compounds in the $, which attract the 

 d" by their odour, should be regarded as specific characters: or in some cases 

 they may be generic characters, possessed by a number of species, which raight 

 explain the fact that cf cT of two species of Dacits are attracted by Citronella oil. 



H. Scott (Cambridge). 



904) Hewitt, C. G. (Canada, Dominion Entomologist), Fa)inia {Homalomyia) 

 canictilaris Linn. and F. scalaris Fab. In: Parasitology , Bd. V, Heft 3, 

 S. 161 — 174, Textfig. 1—7, 1912. 



This paper is "an account of the bionomics and the larvae of the flies and 

 their relation to myiasis of the intestinal and urinary tracts". F. cankularis is 

 the less common of the two species of flies found in houses: it is more abundant 

 than Musca domestka for a short time in May and June, but with the advent of 

 hot weather M. domestica greatly exceeds it in numbers. In a number of large 

 collections of house-flies made in various localities in England, and at Washington, 

 the number of jP. cnnicularis varied from 1 to nearly 24% o^ the total, the re- 

 mainder being almost entirely 31. domestica. In houses the S appear to greatly 

 outnumber the 5, sometimes constituting 75 to 85% of the total number of 

 F. canicidaris found within doors : but this does not indicate that J" outnumber $ 

 in the total existing number of the species, for 5 are more usually found out-of- 

 doors, especially near the breeding-places. The larvae breed in decaying animal 

 and vegetable matter and in excreta: they have also been recorded as living in 

 caterpillars (of Fpischmia canella), in the nest of a Bomhus, in old birds-nests, etc. : 

 they are found from May to October. The larval period may last a week, or 3 

 or 4 weeks if the food-substances become dry. Before pupating the larvae leave 

 very moist substances in which they may have been living and seek drier situa- 

 tions: the pupal period lasts from 1 to 3 weeks or even more; larvae which have 

 developed very late may pass the winter in the pupal state. The larva and its 

 various forms of remarkable spiniferous processes, etc., is described and illustrated, 

 and descriptions are also given of the c? and ? fly. 



F. scalaris is very common in latrines. Its habits are somewhat similar to 

 those of F. cankularis, but it prefers excrementous matter as a nidus for its eggs, 

 and is very commonly found in human excrement. The larvae emerge as early 

 as 18 hours after oviposition, and become fuU-grown in 6 — 12 days. The least- 

 recorded duration of the pupal period is 9 days. The larvae seek drier situations 

 in which to pupate. A description of the cT and $ fly, and the points in which 

 they differ from F. canicuJaris, is given. The larva is also described and illustrated, 

 the more feathery, pinnate character of its spiniferous appendages being clearly 

 seen. This species breeds more commonly in human excrement than F. canicularis, 

 and is more commonly the cause of intestinal myiasis. 



A number of records is given (pp. 171, 172) of the occurrence of the larvae 

 in the stomach and intestines of human beings, of their effects, and of the ex- 

 pulsion of the larvae, often in large numbers, either by vomiting or per anum. 

 In one of these cases it appears that the larvae had entered the stomach in the 

 egg-state and after hatching passed on to the intestines. The writer considers 

 that infection of the alimentary tract may occur either by way of the mouth or 

 per anum (p. 173). Cases of myiasis of the urinary tracts are also mentioned, 

 and possible modes of infection are discussed. A bibliography of literature on 

 myiasis is added (p. 174). H. Scott (Cambridge), 



