46 ILLINOIS BIOLOGICAL MONOGRAPHS (364 



The three genera studied can be separated as follows: 



1(2) Body large, stout, longer than 24 mm.; markings mottled with dark brown and 

 yellowish irregular spots, without brownish stripes or black spots; setae on head 

 small, slender, those on genae similar to other setae, not spinous; head blackish. 



Diprion Schrank. 



2(1) Body smaller, slender, usually shorter than 24 nam. ; markings not mottled, but with 

 brownish longitudinal stripes or rows of black spots 3. 



3(4) Third abdominal segment with annulets 1, 2 and 4 with setae and glandubae; setae 



on head stiff, long, spinous, those on genae often very large and spinous 



Neodiprion Rohwer. 



4(3) Third abdominal segment with annulets 2 and 4 with setae and glandubae; setae on 

 head microscopic, and very few in number Monocknus Dahlbom. 



Neodiprion Rohwer 



Larvae rather large; length about 19-24 mm.; body slender, with longi- 

 tudinal brownish stripes or rows of black spots along subdorsal, supra- 

 spiracular, and sometimes subspiracular lines; head round in contour, 

 cephalic and caudal margins parallel in profile; front flattened, subpenta- 

 gonal, as high as wide; ocularia large; antennaria subequal in diameter to 

 ocularia, their own diameter apart; labrum semicircular, with small 

 crescentic median emargination; mandibles sharply dentate, the dextral 

 with four dentes and the sinistral with five; maxillary palpi large, four- 

 segmented, segments 1-3 ring-like, successively diminishing in diameter, 

 segment 4 suddenly and distinctly smaller than the preceding segment, 

 conical, bluntly pointed; galea chitinized, digit-like, smaller than palpi; 

 lacinia thick, lobate, bearing a minute triangular blade-like seta on ventro- 

 mesal angle, a stiff seta on dorso-mesal angle, and a row of three to five 

 minute setae on the oblique cephalo-mesal margin; labial palpi normal, 

 segment 2 usually longest, segment 3 conical, suddenly and distinctly 

 smaller than preceding segment; totaglossa with dorso-cephalic depression 

 on the meson and with several minute sensory pits; parapharynx distinct, 

 linguiform, constricted dorsad of the middle by a pair of chitinized pieces; 

 thoracic legs well developed, normal in form, usually blackish, segments 

 strongly chitinized, coxae largest, trochanter ring-like, chitinized on the 

 caudal two-thirds, with a whorl of setae, distad of setae membranous, 

 femur smaller than trochanter in diameter, entirely chitinized, wider than 

 long on dorsal aspect, increasing in diameter distad, tibia subequal in length 

 to femur but smaller in diameter, tarsal claws small, basal portion of claw 

 undeveloped, all segments of leg membranous on the ventral aspect, 

 prothoracic legs one-half the size of metalegs, mesolegs slightly smaller 

 than the latter; third abdominal segment with annulation formula, 2, 1, 

 (3, 5, 6), 5; spiracle on annulet 2, annulets 1, 2 and 4 with a transverse 

 row of slender, cylindro-conical glandubae, annulet 2 with a few micro- 

 scopic setae; substigmatal and surpedal lobes large, with several glandubae 



