- 
INSECTS INJURIOUS TO MUSHROOMS. 5 
young or developing caps. They hatch’ in a short time into the char- 
acteristic six-legged young, which rapidly mature to adults similar to 
the one in figure 2._ The time from the deposition of the ege to the 
maturity of the mite has not, to the writer’s knowledge, been accu- 
rately worked out, but undoubtedly occupies only.a few days. It is 
on this account that the mite is able to increase so rapidly, apparently 
as if by magic, and thus give rise to the theory of spontaneous genera- 
tion sometimes advanced to explain this condition. 
Under certain conditions the hypopus or migratory stage 1s pro- 
duced. This stage, according to Banks,’ is peculiar to the family 
Tyroglyphide, to which this mite belongs, and is quite remarkable. 
The mite develops a hard, chitinous covering, has no mouthparts, and 
is provided with short legs insufficient for walking. On the ventral 
surface of the body is an area provided with sucking disks, by means 
of which the hypopus attaches itself to an insect and is so transported 
to suitable breeding grounds in other localities. On arrival at a suit- 
able breeding place the mite detaches itself from its insect host, molts, 
and soon becomes adult. During the hypopus stage the mite takes 
no food and causes no injury to the insect which carries it. This 
peculiar stage is the natural means for the distribution of the mite to 
new localities, and is in many cases responsible for its appearance in 
localities far from previously infested beds. 
In addition to the way mentioned above, the mite may obtain 
access to mushroom houses in infested compost or in spawn from 
infested houses. However, the greater part of the infestation prob- 
ably takes place through the agency of the small flies which frequent 
mushroom houses and which carry the hypopus stage of the mite 
from one house to another. 
REMEDIES. 
Little can be recommended for the control of the mushroom mite 
after it has once become established in a house. Owing to the ab- 
sence of breathing-pores it is little affected by the fumigants suitable 
for the control of the other mushroom pests, while applications of 
sulphur, tobacco dust, and other suitable insecticides to the beds 
seem only to prove slightly inconvenient to the mite. It is one of 
the most stubborn pests with which we have to deal in mushroom 
culture, and may be brought into the house in almost any manure 
that is used for the bed. When in the hypopus stage it is capable of 
prolonged suspension of vitality and is likely to remain in the house 
for an unlimited time without death. The only measures, therefore, . 
that may be considered are those of prevention. 
When a house becomes infested, all compost should be gathered 
with the utmost care, removed to the outside, and thoroughly disin- 
1 Proc. U. S. Nat. Mus., vol. 28, p. 79, 1904. 
