INTRODUCTION. 11 
palpi from four to six jointed. The maxillary lobes are broad and membranous, 
while the ligula is fleshy, and either rounded or square at the end. There is a com- 
plete costal cell, while the subcostal cells are incomplete. The egg is of large size, 
and increases in size as the embryo becomes more developed. The larva is a short, 
thick, fleshy, footless grub, with the segments of the body rather convex. When 
hatched they immediately attack the interior of the gall, which has already formed 
around them. Many species transform within the gall, while others enter the earth 
and there become pupae. 
Like the Aphides and certain other insects, the females often repro- 
duce parthenogeuetically, viz, they lay eggs without having paired with 
males, the latter not being at the time in existence. Thus the late B. 
D. Walsh * discovered that the autumn brood of a gall-fly (Cynips quer- 
cus-aciculata) consisted entirely of females which laid eggs, producing 
the following spring both males and females which were originally re- 
ferred to a supposed distinct species (Cynips quercusspongifica). Hence, 
after several experiments Mr. Walsh declared that u the agamous 
autumnal female form of this Cynips (G. q.-aciculata) sooner or later 
reproduces the bisexual vernal form," and is thus u a mere dimorphous 
female form" of C. q.-spongifica. It was reserved for two other Ameri- 
can students of the gall-flies to establish the fact that an alternation 
of generations takes place in these insects. The case is thus stated by 
Mr. L. O. Howard, in Psyche (in, 329, June 24, 1882). 
America may justly claim the credit for the discovery of this most interesting fact 
of alternation of generations among Cynipids. Kiley, in the interjected remarks in 
his article on "Controlling Sex in Butterflies" (American Nat., Sept., 1873, v. 7, p. 
519), was the first actually to establish the fact beyond all perad venture, asM. Lichten- 
stein points out; yet Bassett, four months previously (Can. Entomologist, May, 1873, 
vol. 5, p. 93) had stated, in the following words, the theory which Adler has so fully 
verified : "From all the above facts I infer that all our species that are found only in 
the female sex are represented in another generation by both sexes, and that the two 
broods are, owing to seasonable differences, produced from galls that are entirely 
•distinct from each other." In this article Bassett has just missed the actual proof in 
two instances. With Cynips q. -operator he had observed the females of the vernal brood 
ovipositing in acorn cups and producing the gall q.-operatola of Riley's MS.; but 
he failed to rear the flies from these galls and so missed the complete proof. In the 
case of C. q.-batatus Bass., he had bred the sexual forms from leaf galls, and the agamic 
females from twig galls, but had not actually observed the females of the former in the 
act of ovipositing in the twigs ; thus again missing the proof. Riley, however, as he 
tells us in his published note, succeeded in breeding the agamic females of q. -operator 
from the acorn galls ; thus, in connection with Bassett's observation of the oviposi- 
tion, completely establishing the fact of alternation. So the credit should be joint. It 
is, in fact, much like the well known case of Siredon and Amblystoma, in which the 
credit should be divided between Baird and Dumeril. Dr. Adler very excusably 
overlooked this note of Riley's. Walsh, in his earlier articles, came no nearer the 
actual state of the case than to prove that two females, formerly described as dis- 
tinct species, may belong to the same male. 
Independently of and subsequently to the work done in the United 
States, Dr. Adler, of Germany, also discovered and satisfactorily 
* American Entomologist, ii, 330, October, 1870. 
