1887] . Entomology. — 579 
would again be taken and mated, and so on, for several genera- 
tions. (2) Exactly the same process just described would be 
gone through, after substituting throughout the words ‘ medium- 
sized’ for ‘largest.’ (3) Similarly, after substituting the word 
for ‘largest.’ The result will be to obtain a precise 
measure of the diminution of rate at which a divergence from 
h erage race proceeds in successive generations of 
continually-selected animals.” —Extomologist, vol. xx p. 60. 
. 
Ears of Insects.—A correspondent calls attention to the state- 
acter. .. . As to their probable functions, we possess no satis- 
factory indication; but it seems particularly improbable that 
they are auditory organs.” And again, “It is certain that they 
are of much importance, but their physiological rôle is, we repeat, 
follows: “I find that, by leaning too heavily upon a 
~ writes as foll 
considerable amount of negative evidence collected last year 
and the year preceding, I made an error last summer in the life- 
history of the corn plant-louse, Aphis maidis. We have suc- 
ceeded this spring in finding the eggs of this species in the nests 
of Lasius alienus, in fields of corn infested by the lice the pre- 
-vious year, have hatched these eggs in the office, and have reared 
