ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 567 



Arthropoda. 

 a. Insecta. 



Bionomics of the House-fly.* — C. G. Hewitt publishes the third 

 part of his tine study of the structure, development, and bionomics of 

 the house-fly, Musca domestica. This paper deals with the habits of the 

 house-fly, its allies, its enemies (parasitic and other), and finally its 

 relation to human disease. The distribution of M. domestica is almost 

 world-wide, for it has apparently followed man everywhere. In this 

 country it is by far the commonest species, and may be almost the only 

 one in warm kitchens, etc., where food is present, but in other rooms the 

 lesser house-fly, Hamalomyia canicular is, is often abundant, and sometimes 

 predominates. In country houses Stomoxys calcitrans, which is not a 

 house-fly in the strict sense, is often the dominant species. The author 

 gives some account of the life-history and the breeding-places of other 

 species occurring as co-inhabitants of houses, and then proceeds to dis- 

 cuss the physiology of Musca domestica. 



Reference is made to previous papers in regard to the influence of 

 food, temperature, and light, and the bearing of these on the question 

 of hibernation is indicated. While the great majority of the flies 

 observed in summer are killed off or die naturally on the approach of 

 winter, some, apparently the most recently emerged, hibernate through- 

 out the cold weather. Dissection showed that the abdomens of hiber- 

 nating individuals are packed with fat cells, the fat body having developed 

 enormously, and that the alimentary canal shrinks into a very small 

 space. Dark places are sought out and many flies hibernate between 

 the wall-paper and the walls of living rooms. Hibernation is more or 

 less complete according to temperature, and the same factor determines 

 the time of emergence in spring. Flies, though capable of fairly long 

 flights, do not normally fly far from their breeding-places, but they may 

 be borne by the wind for considerable distances. Experiments in regard 

 to regeneration showed that broken wings and legs are not re-grown, 

 although the wing has been known to be regenerated in the case of a 

 newly pupated fly. 



By far the most important of the natural enemies of the house-fly is 

 the fungus Empusa mascse Cohn, which kills off great numbers in 

 autumn. It may be recognized as a whitish ring of fungal spores sur- 

 rounding the dead body of a fly attached to a wall or window-pane. 

 The life-history of the fungus is described, and it is suggested that it 

 might be artificially cultivated and disseminated so as to rid us of the 

 flies at the beginning instead of at the end of summer. An Arachnid, 

 Chernes nodosus, and certain mites are frequently found firmly attached 

 to the bodies of flies, but there is not sufficient experimental evidence to 

 show whether these are really parasitic, or whether they merely use 

 their hosts as a medium of transportation. The investigator found within 

 the head region of two of the flies dissected the Nematode worm Habro- 

 nema muscse, seen by Carter in Bombay, but not previously recorded for 

 this country. 



The last part of the paper contains a discussion of the probabilities 



* Quart. Journ. Micr. Sci., lxiv. (1909) pp. 3-47-414 (1 pi.).; 



