G. S. Graham-Smith 
511 
with marked rings of white growth between the segments (Plate XXVIII, 
figs. 1-8), and within 15 hours a halo of spores may surround the 
specimen. If the fly is protected from wind currents the directions in 
which the spores are discharged are clearly indicated by the contour of 
the halo, as is shown in photographs of such specimens on Plate XXVIII, 
figs. 9, 10, 11. The spores seem to be discharged mostly from the 
abdomen, forming a well-marked circle, incomplete only in front of the 
head, of a diameter of 1| inch round the fly. The spores may reach 
objects J inch above the insect. 
The growth of the fungus seems to be most rapid and complete in 
warm damp weather, but the optimum conditions of humidity and 
temperature have not been ascertained. On the other hand its progress 
may be fairly rapid even in cold weather, for on a fly confined in cage I, 
which first showed signs of infection on Nov. 16, marked white bands 
had developed by Nov. 18. During this time the maximum temperature 
recorded in the shade was 43° F., and the minimum on the grass varied 
between 20° and 22° F. 
Mites. 
In the course of these investigations two species of mites, one much 
larger than the other, came prominently to notice. Mr C. Warburton 
very kindly examined some of the specimens and reported that the 
smaller specimens were adults, belonging to the genus Holotaspis, and 
the larger, nymphs of the genus Gamasus, differing slightly from 
G. coleoptratorum. 
The Holotaspis, which seems to be parasitic, was found on several 
of the common species of flies, being especially frequent on the house-fly, 
M. domestica, 0. leucostoma and H. dentipes. Often only a single parasite 
is found on a fly, attached in almost any situation. The anterior part of 
the ventral surface of the abdomen is a common situation, but the mite 
may be found on the thorax, head or leg. Specimens were even fo un d 
attached between the eyes and on the distal end of the proboscis. Not 
infrequently, however, several are found on one fly, and then the 
individual mites may occur in different situations, or in a cluster. 
For example a specimen of 0. leucostoma had one mite on the dorsum 
of the thorax, another at the base of the first pair of legs and a third 
at the base of the third pair, while one specimen of M. domestica had 
a cluster of four mites attached to the ventral surface of the abdomen, 
and another had a cluster of five on the upper surface of the thorax. 
In such cases the mites are often so close together that they appear 
