324 PSOE. 
there is a regular pulsating movement in 
the dorsal vessel, and in the small four- 
chambered bodies in the 9th segment 
[ovaries]. The entrance of air into the 
posterior pair of spiracles seems to give 
the initial impulse which travels so rap- 
idly along the series and its ramifications 
that almost immediately the head of the 
insect begins to move from side to side 
as if affected by the same influences 
which affected the other parts. This oc- 
curs when the leafy covering of the lar- 
ya is cut open and light and air admitted. 
The first conscious effort of the larva 
when its sheath [nest] is opened is di- 
rected toward the elaboration of silk 
fluid with which to enclose itself once 
more within its case. With this purpose 
it eats rapidly and the silk fluid is seen 
at the same time accumulating in and 
near the thoracic segments. The larva 
uses its short, black, front pair of feet to 
unite the threads which it spins back 
and forth, forming a cord of 40 to 75 
threads, as may suit its purposes. 
The pupa exhibits no specially inter- 
esting features. It is pale green, with 
faint traces of the outer set of tracheae 
still visible ; broad at anterior end, with 
a sharp black spine from its extremity, 
by which it is attached to a mass of fine 
white silk. Body cylindrical, tapering 
A loose girdle of silk pas- 
ses around its body, and its entire length 
rests against a delicate iayer of white 
silk. If disturbed it moves with great 
rapidity. It transforms in ten days. 
The motions of the imago of this hespe- 
at anal end. 
perian are very rapid. 
I have not sufficient data to make this 
an exhaustive monograph, but other stu- 
dents may have added what I have omit- 
ted. If not. we may leave to time and 
diligence the further discovery of such 
facts as are yet unknown. 
CIRCULATION OF BLOOD IN THE.LARVA OF HYDROPHILUS. 
BY GEORGE DIMMOCK, 
EXAMINATION Of living larvae of Hy- 
drophilus under the microscope, the past 
summer, revealed the 
blood in their antennac and trophi, which 
is so distinctly visible and so curious in 
its directions as to be worthy of notice. 
The blood of the larva of Hydrophilus, 
after leaving the anterior extremity of 
the dorsal vessel or heart and entering 
the head, divides itself into two lateral 
branches, one of which descends on 
each side of the oesophagus, the two 
branches reuniting beneath the oesoph- 
agus, a little anterior to their division 
on its upper side, to form a median 
circulation of 
CAMBRIDGE, MASS. 
stream. Between the point where the 
streams separate and reunite, each 
stream gives off three branches, all of 
which flow in the same direction as the 
middle stream formed by the reunion 
of the two lateral streams, that is, tow- 
ard the anterior part of the head. The 
median stream formed by the reunion of 
the two lateral streams, which is, of 
course, more ventral in position than the 
six other streams, enters the middle of 
the labium, and passes along the dorsal 
half of that organ until it nearly reaches 
the bases of the labial palpi. Here the 
stream turns back laterally and ventrally, 
SS 
