23 
varied from eighteen to an indefinite number of days—forty-three 
days was the maximum age for those kept under the lower tempera- 
tures. The number of young produced by a single female varied 
considerably and variation was greater among individuals under 
like conditions than among those under variable conditions. The 
number varied from just a few to 270. From 3 to 8 males were 
usually produced, there being two exceptions to this: In one instance, 
when the temperature was between 70° and 80° F., 26 males were 
produced and in another case a large number. The firstborn in many 
cases were males. The largest number of young produced during 
any one day by a single female was 52. 
The ideal temperature for rapid development and the production 
of the maximum number of young was from 70° to 80° F. The ab- 
domen of the female reaches its maximum size in about five days. 
The mite is omnivorous, preferring smooth larve to hairy ones. A 
young mite can not enter a closed Isosoma cell. Mites can live only 
a short time without food—less than a day in all cases observed. 
Copulation occupies only a few minutes, the males rarely leaving the 
surface of the abdomen of their mother. In the laboratory a single 
Isosoma pupa or larva will sustain a female up to the time she pro- 
duces young and continue to support her progeny for from twenty 
to twenty-eight days. In the field, or under natural conditions, 
one pupa would probably furnish food for live mites for approxi- 
mately the same length of time, as in one experiment a pupa furnished 
sufficient food for a month. The mites can be kept alive by subject- 
ing them to a low temperature and development checked for an 
indefinite time. When attacking human beings they do not bury 
themselves in the skin and remain there as do the ‘“‘chiggers.” 
PREVENTIVE AND PROTECTIVE MEASURES. 
Throughout the territory involved in the eastern epidemic of this 
dermatitis, which was due to the excessive abundance of the Angou- 
mois grain moth, the evidence recently obtained by the writer has 
been overwhelmingly to the effect that where wheat was thrashed 
as promptly as possible after harvest and directly from the shocks 
in the field, almost no occurrence of this grain moth, without which 
there would be no mites, was observed by millers and others han- 
dling the thrashed grain. On the other hand, when hauled from 
the field and placed unthrashed in the barn, the damage from this 
pest has varied up to nearly 50 per cent, and has so affected the 
crop as to cause its rejection by millers, except where ground on 
the farmer’s order. Here, then, is a means of protection for people 
who use or handle wheat straw grown in this section of the country. 
In Ohio, Indiana, and Illinois, where the mite causing this der- 
matitis has increased enormously on account of the prevalence of the 
[Cir. 118] 
