[aussow] PARASITISM OF ISARIA FARINOSA 97 
was kept in the dark under ordinary laboratory temperature. In about 
22 days a considerable quantity of sporophores of the Jsaria were 
produced. Originally 23 cocoons showing the white patches of the 
fungus were placed in the cage. No adult insect emerged from these 
cocoons. Some of the cocoons were dissected at intervals and were 
found to contain a blackened or dirty yellowish adult. The dissected 
cocoons were replaced and the /saria developed further. I then ob- 
tained a handful of cocoons which were carefully examined and which 
showed no signs of an infection whatever. They were divided in equal 
numbers, 30 cocoons serving in each of the following experiments :— 
EXPERIMENT A. 
These sound living cocoons were introduced into a breeding chamber 
and were carefully kept free from external infection from /saria spores. 
It was sought to ascertain how many of the cocoons would produce 
living adults and those emerging were carefully recorded. Ten adult 
larch sawflies emerged in the course of ten days. Eleven parasitic 
insects were also found to emerge from the cocoons; the remainder 
of the cocoons did not “hatch” at all. Some of these were found, on 
dissection, empty. Some showed remains of a dead adult. Only one 
cocoon showed signs of [saria. 
EXPERIMENT B. 
The same number of cocoons were used. These were placed, 
together with infested moss and /saria spores bearing cocoons, into a 
small breeder. After 10 days 6 adults and 6 parasites were observed 
and were left confined in the cage. One of the first peculiar symptoms 
observed in these cocoons was a darkening in colour of 16 of them. 
The colour of the normal cocoons being light chocolate, while in these 
cases the colour was of a pronounced dull chocolate tinge. Four more 
adults emerged on subsequent occasions. Although no signs of Jsaria 
were then noticeable on the darkening cocoons some of them were 
dissected and microscopically examined. Two of the examined cocoons 
showed the interior walls lined with white fungus hyphæ; others showed 
fungal hyphe in the dead adults’ body. Later on white fluffy patches 
occurred externally rather suddenly on most of the remaining cocoons. 
From the appearance of these fungous growths it was evident that they 
were formed by the Jsaria. About two months after beginning the 
experiments the fungi formed the well-known forked sporophores and 
the microscopical characters proved the fungus to be Jsaria. Spores 
had been produced abundantly at very early stages and no doubt had 
become disseminated throughout the cage. When about three months 
