46 THE CANADIAN ENTOMOLOGIST. 



the thoracic joints between the white subdorsal and substigmatal h'nes ; 

 tubercle IVa now occurs on joint ten, at the upper corner of spiracle, is 

 slightly larger than IV on this joint, but smaller than IV on the preceding 

 one; I and II small on all joints to eleven. 



Stage V. — Similar to preceding, colours intense, lines sharply 

 defined, joints four, five, six and seven show as a solid girdle of blackish- 

 purple, except where crossed by dorsal line. Tubercle IVa on joint ten 

 as before. 



Penultimate stage. — Similar, except the ground colour fades to a 

 lighter shade; tubercles the same, IVa holding its corresponding size, 

 and is without seta. 



Mature larva ; head normal, smooth, polished, now becomes 

 brownish-yellow, side marking lost, though shield holds its conspicuous 

 black edging ; ocelli and mouth-parts touched with black ; epicranial 

 setae normal, of about equal length, IV seeming longest, adfrontal area 

 defined by nearly straight sutures ; thoracic shield wide as head, long as 

 joint one, smooth, shining, yellowish-brown ; anal shield forms similar 

 protection to joint twelve, but its surface is minutely roughened with 

 granulations ; tubercle IV is largest on first ten segments, exceeding the 

 spiracle, on joint eleven III slightly exceeds IV, as do I and II, on joint 

 ten IVa still holds the size of true IV lower down ; all are brownish- 

 black ; spiracles dull black ; crochets of prolegs similar to harrisii ; body 

 colour has now faded to whitish translucence, all lines lost ; length of 

 larva per stages, 6, 9, 12, 20, 26, 34, 42 mm. Larval period fifty to 

 fifty-six days. 



The boring is forsaken usually, and the pupal period, covering twenty- 

 eight to thirty-six days, is passed in the ground or beneath some slight 

 covering of refuse. The pupa is shining brown, the wing-cases well 

 defined and thin enough that the stigmata are plainly seen shortly before 

 emergence; abdominal joints taper evenly; a slight bifidate spur. 

 Length, 18-22 mm. 



Among the yellow-brown species of the genus of which it is a good 

 type, arctivorens comes closest to the yellow, or type form of harrisii. 

 both in larva and imago. Its individuality seems most pronounced in the 

 white marking formed by the orbicular and claviform, being proportion- 

 ately larger than with its allies, a feature especially accentuated in dwarfed 

 or abnormal examples. There is no erratic variability as occurs with 

 harrisii. The genitalia are of the usual pattern, showing no distinguish- 

 ing features. 



