510 Observations on Habits and Parasites of Common Flies 
almost without interruption till Nov. 7, when there were still 30 flies 
alive, none of which subsequently developed the disease. The death 
rate reached its maximum between Oct. 18 and 25, the period during 
which the first outbreak was noticed in cage I. It may be worth noting 
that the disease had come to an end in cage II before the second 
outbreak occurred in cage I. 
Altogether 1049 flies were placed in cage II and 281 or 26-7 % died 
with well-marked signs of the disease. It is quite possible that besides 
these some others died of the disease without showing recognisable 
signs. 
Concurrently with these observations a careful watch was kept for 
the disease amongst the flies which entered various rooms in the house, 
and more especially amongst those which were allowed to live un¬ 
molested in the kitchen. Owing to their frequent migrations it was 
impossible to ascertain the percentage of flies in the kitchen which 
succumbed to the disease, but the mortality from the disease, as 
ascertained by noting cases of the disease indoors, seemed much smaller 
than amongst the flies kept out of doors. Possibly a number of those 
which migrated out ultimately died of the infection. Two cases occurred 
on Aug. 30, the date on which the disease started in the large fly cage. 
After this a long period elapsed before the next case occurred on Oct. 4. 
Three weeks later on Oct. 25 the first of a series of six cases, occurring 
between that date and Nov. 6, was noticed. Though flies were present 
in decreasing numbers up to Dec. 12 no other specimens with the 
disease were seen. 
No previous attempt seems to have been made to ascertain with 
any degree of accuracy the mortality due to this disease. 
Ample opportunities were afforded for observing the progress of the 
disease under natural conditions, and in some cases flies in the earliest 
stages were confined in glass boxes and watched. The first recognisable 
sign of the disease is an appearance of stiffness. The fly’s legs are 
disposed in abnormal attitudes, and the insect is sluggish and remains 
in one place, though it is capable of moving in an awkward wav when 
touched. Next white rings of growth begin to appear between the 
segments of the abdomen, but before the disease has made much further 
external progress the fly dies. 
Under suitable atmospheric conditions the fungus grows with great 
rapidity after the death of the fly, and spores are discharged around the 
insect’s body. A fly which only appears stiff and sluggish when attention 
is first attracted to it may show in 4 or 5 hours distention of the abdomen 
