22 
In the light of the foregoing, it would appear that the only way 
to evade the disorder among human beings caused by this mite lies 
in preventing the occurrence of these two destructive grain insects 
which are responsible for the abundance of the mite itself. There is, 
therefore, a double incentive for the farmer to use every effort to 
prevent the occurrence of these pests in his fields. In many fields 
in Ohio Mr. Wildermuth found that more than one-half of the straws 
had been attacked by jointworms, and the damage resulting from their 
attacks amounted to a considerable percentage of the farmers’ wheat 
crop. (See fig. 13.) In addition to this—and we now know that this 
mite is generally present—his 
own family and employees 
suffer the annoyance of this 
dermatitis and also those who 
attempt to use mattresses into 
which the infested straw has en- 
tered. Thus people hundreds 
of miles away, unaware of the 
presence of these mites in mat- 
tresses, are caused not only 
great aggravation but intense 
suffering through their use. 
DEVELOPMENT OF THE MITES. 
The investigations carried 
out during the winter of 1909— 
1910 by Mr. Wildermuth reveal 
the fact that a period of from 
Fig. 13.—Reduction in yield of wheat attacked by joint- . s = 
worm (Jsosoma tritici). The tube at left contains yield six to an indefinite number of 
from 100 heads from uninfested straws; tube at right days elapses between the time 
Pouieions from 100 heads from infested straws. a female emerges from the ab- 
domen of the mother until it 
produces young. This depends upon temperature. 
For a temperature of from 90° to 100° F., six days elapses; for a 
temperature of from 80° to 90° F., seven days elapses; for a temperature 
of from 70° to 80° F., nine days elapses; for a temperature of from 
60° to 70° F., thirteen days elapses, and for a temperature of from 
50° to 60° F., twenty-eight days elapses. 
With temperatures lower than 50° F. it is doubtful if the mites 
would develop. The periods required for the development of differ- 
ent females subjected to the same temperature are very uniform. 
(For instance, in temperatures of from 70° to 80° F. nearly every 
female produced young in exactly nine days.) The life of the mites 
[Cir. 118] 
