6 
BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. 
The size of the prepupa is discussed under "Larval ins tars." 
The prepupa of Diprion simile is similar to the larva, in structure, with the armature 
or spines reduced to indistinctness. The head is grayish white, eye disks and 
apices of mandibles, only, black. The thorax and abdomen are both pale greenish 
white, with narrow green, dorsal longitudinal stripes and broader green supraalar 
to alar longitudinal lines which are broken by yellowish spots on B, C 1 , C 2 , the pale 
spiracular area, and the yellowish alar area. Pleurum pale but for a pair of greenish 
pleural spots. Venter, uropods, postpedes, anus, and epiproct pale, the latter faintly 
gravish. 
COCOON. 
The cocoons (Fig. 5) of Diprion simile are cylindrical, with hemispherical ends. 
They are single-walled, of fine texture, rather glossy, fairly stiff, but thin. Cocoons 
from which males emerge are somewhat smaller than those from which females issue, 
7 by 3.5 millimeters being the size of the former, while the latter are 9.3 by 4 mili- 
meters. The cocoons are usually dark brown; sometimes they are pale tan when 
made but become dark brown within a week or 10 days, and in one instance a whitish 
cocoon was spun which failed to become colored. 
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Fig. 4.— Diprion simile: Larval growth charts. Stage of larva indicated by large figures. Female has 
six stages, male five. Growth records are shown for a single female and a single male larva. 
In captivity the cocoons were often spun on the needles, and 
while this may be the rule in nature the writer is inclined to believe 
that many of the prepupa of this species, like those of Neodiprion 
lecontei, will make their cocoons in the ground for the sake of the 
protection thus afforded in winter. This view is supported by a 
European observation 6 which records the summer brood cocooning 
on the branches of the tree while the winter brood makes its cocoons 
beneath the tree. 
The cocoon is spun of a " silken" thread from the vicinity of the 
mouth. 7 The end of the cocoon inclosing the caudal extremities of 
the prepupa is made first, then the anterior end is inclosed by a 
sidewise motion of the head. After the entire cocoon is formed 
the prepupa works over the inside, plastering a sticky substance to 
it. This coating makes the glossy inner surface. 
« Britton, W. E. A destructive pine sawfly introduced from Europe. In Jour. Econ. Ent., v. 8, no. 
3, p. 379-382. 1915. See p. 381. 
* This thread doubtless comes from the apex of the labium, where the writer has observed a similar sub- 
Stance protruding in some prepupse of Cimbex americana Leach in his possession. 
