Descriptive-—The adult insect is a phycitid moth with a wing 
expanse of a little less than an inch; the fore-wings are pale leaden 
gray, with transverse black markings of the pattern shown in the 
accompanying illustration (fig. 1, a); the hind-wings are dirty 
whitish, semitransparent, and with a darker border. The larva or 
caterpillar, illustrated at figure 1, c, e, and at figure 2, is whitish with 
minute black dots, and sparsely hairy. When full grown it measures 
about one-half an inch or a little longer (12.5-17.5 mm.). The 
chrysalis, shown at figure 1, d, is reddish brown. 
Distribution.—Until the year 1877, when the moth was discovered 
in a flour mill in Germany, this insect was comparatively unknown. 
Later it invaded Belgium and Holland, and in 1886 appeared in 
England. Three years afterwards it made its appearance in destruc- 
tive numbers in Canada. In 1892 it was reported injurious in mills 
in California, and in 1895 in New York and Pennsylvania. 
From that time forward until 1904 the dissemination of the species 
was comparatively slow. In 1898 it had reached Minnesota, the 
next year Wisconsin; in 1900 it had greatly increased in Minnesota; 
two years later it invaded Michigan, and by 1904 it was reported in 
several other States, including Indiana, Illinois, Montana, Colorado, 
Ohio, and Iowa. In later times, each year has witnessed a similar 
increase in distribution, until now, in 1910, this flour moth is attract- 
ing more attention than any insect that ever infested mills or other 
buildings where cereals are stored; indeed, it is almost the sole topic 
of complaint of millers at the present writing, correspondence in 
regard to weevils and flour beetles, which was at one time heavy, 
having fallen off very noticeably. 
Ravages and habits.—The caterpillars form cylindrical silken tubes 
in which they feed, and it is largely due to their habit of web spinning 
that they are so injurious where they obtain a foothold. Upon 
attaining full growth the caterpillar leaves its original silken domi- 
cile and forms a new web, which becomes a cocoon, in which it 
undergoes transformations to pupa and to imago. While searching 
for a place for transformation the insect is most troublesome. The 
infested flour becomes felted together and lumpy, the machinery 
becomes clogged, necessitating frequent and prolonged stoppage, and 
resulting in a short time, in large establishments, in the loss of thou- 
sands of dollars. A sample of matted flour is illustrated in figure 3, 
from a photograph by Mr. C. H. Popenoe. 
As to the losses caused directly and indirectly by this insect it has 
been difficult to obtain estimates, the lowest being between $100 
and $200 to a mill of 1,000 barrels capacity. The average loss due 
to closing down the mill and cost of treatment seems to be not far 
from $500 for each fumigation, “‘to say nothing of the loss to busi- 
ness,” according to one Kansas milling firm. An estimate of $1,000 
[Cir. 112] 
