4 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. 
and C with a few setae or spines ; A of the prothorax bare and constricted and D bare ; 
alar area wanting or incorporated in the spiracular area of the prothorax, large in the 
mesothorax and metathorax; in the pleurnm, preepipleurite large, well defined, and 
possessing setae or spines; postepipleurite large, well defined, spined in prothorax but 
bare in mesothorax and metathorax; prehypopleurite large, triangular, of heavy 
chitin and sparsely, finely haired; posthypopleurite large with a prominent spined 
lobe; legs with 4 joints and an apical claw, joint 3 with small soft pad on inner side 
at apex. Abdomen with the tergum of urites 1 to 9 inclusive composed of areas A, B, 
C l , C 2 , C 3 and D; A, B, and C 2 spined, C 1 , C 3 , and D bare; urite 10 consists tergally 
of the epiproct, which is rather thickly spined and without pseudocerci; spiracular 
area present on urites 1 to 8, wanting on urites 9 and 10; alar area present on urites 1 
to 9 (reduced on urite 9), absent or indistinct on urite 10; the pleurum with preepipleu- 
rite and postepipleurite distinct, rather large and spined on urites 1 to 8, reduced, 
indistinct, but spined on urite 9, wanting or indistinguishable on urite 10; hypopleu- 
rite distinct but not divided into prehypopleurite and posthypopleurite, unspined 
and bearing the uropods on urites 2 to 8 inclusive, indistinct or wanting on urites 1, 
9, and 10; uropods well developed on urites 2 to 8 inclusive, not developed on urites 
1 and 9, and developed as postpedes on urite 10. The head is black and shiny, with 
the eyes yellowish and the membranes about antennae, mandibles, trophi, and between 
labrum and epistoma whitish. The thorax is yellow, much darkened with velvety 
black which becomes greenish with growth and age; legs black. The abdomen is yel- 
low, marked as thorax ; uropods, postpedes, ventral region, and anus undarkened. Most 
of the body, the tergum and pleurum of the thorax and abdomen is a mottled black and 
yellow of rather regular pattern. The depressed portions of the body wall are black 
and the raised portions are yellow, giving much the appearance of a yellow larva 
dipped in some adhesive black coloring matter and then allowed to wear off the mate- 
rial darkening its more prominent areas. 
LARVAL INSTARS. 
In the study of Diprion simile the experiments on the larvae 
offered an excellent opportunity to determine the number of larval 
instars and the size of the larvae during each instar. For conven- 
ience, this information is arranged in tabular form below. It will be 
noted that the species has six feeding instars in larvae producing 
female adults and five feeding instars in larvae producing males. 
This feature was remarked upon by the writer in treating Cladius 
isomerus Norton in a recent paper on the subfamily Cladiinae 4 
and is probably common to sawflies, since H. C. Severin 5 records a 
similar difference in the number of instars between larvae producing 
male and female adults in his account of Neurotoma inconspicua 
Norton. 
The prepupa of Diprion simile is rather well defined and differs 
from the larva sufficiently in general appearance to be readily recog- 
nized. 
« Rohwer, S. A., and Middleton, William. North American sawflies of the subfamily Cladiinae. 
"With notes on habits and descriptions of larva; bv "William Middleton. In Proc. TJ. S. Nat. Mus., v. 60, 
art. 1 (no. 2396), 1922. See p. 19. 
» Severin, H. C. The plum webspinning sawfly. State Ent. S. Dak., Tech. Bui. I. 1920. See p. 11, 26, 
tables 2, 3. Severin finds six instars for larvae becoming males and seven instars for those becoming 
females. This larval period, however, covers the entire time spent by the larvse above ground and 
therefore includes the stage recognized in the present paper as the prepupa. 
