116 
early summer at periods varying according to the species of 
beetle, the general advancement of the season, and the character 
of the weather at the time. Warm and genial days in spring 
often bring them suddenly out in myriads where previously only 
scattered individuals have been seen, and their flight at night 
is of course more free when the weather is warm than when 
their energies are chilled by cold and storms. 
In Central Illinois L. fusca is usually the earliest to appear, 
commencing to emerge as early as April 12, and continuing 
alive to June 4. Inversa and hirticula are likely to follow a 
few days thereafter*, and tristis, usually a woodland species, at 
about the same time (May 7 with us to June 7). L. gibbosa 
is relatively late, our earliest specimens having been taken May 
14, and our latest June 25 ; and L. rugosa later still—the latest, 
in fact, of all our very abundant species, ranging from May 18 
in our collections to July 28, at which latter date specimens 
were taken flying at night in Northern Illinois. July 16, an 
imago of this species was observed in Champaign county feed¬ 
ing on a leaf of corn in the field. L . crenulata appears in Illi¬ 
nois in July and August, and, according to Dr. Riley, L. ephilida 
is also a late species, occurring in the same months. (Proc. 
Ent. Soc. Washington, Yol. II., p. 133.) 
As a rule, the males are not only the first to appear but sur¬ 
pass the females in number, taking the season through. They 
also come to lights much more freely than the females, as 
is shown by a comparison of our collections made at lights 
with those made the same night from trees on which the beetles 
were feeding. The 7th of May, 1891, for example, a collection 
of L. inversa made with a lantern trap contained 1,210 males 
and twenty-four females,—a ratio of fifty to one,—while we took 
from trees the same night one hundred and twenty-two males 
and seventy-three females—less than two to one. Taking all our 
collections of this species for the summer of 1891, we find that 
in those from lights (1,418 specimens) the males are to the females 
as fifty-one to one, while in those from trees (271 specimens) 
the ratio was one and one half to one. This is, however, much 
greater than the usual difference in other Lachnosternas, the 
species evidently varying with reference to their sensibility to 
light. L . fusca gave us on the date first mentioned, May 7, less 
than two males to one female (1.6 to 1) at the lantern trap, 
while for tristis the ratio was 1.4 to 1 (79 and 56). L. hirtic¬ 
ula seems to be an intermediate species in this respect. Of 537 
specimens discriminated as to sex, 152 males and 33 females 
Avere taken at lights (nearly 5 to 1) and 194 males and 158 
females on trees (about 1.3 to 1). 
Ho wever taken and at whatever part of the season, it is rarely 
that the females exceed or even equal the males in the same col¬ 
lection. Throwing together 2,600 specimens of several species, 
* April 29 is our earliest date for each, and June 24 is our latest for hirticula and June 28 
for inversa. 
