THE CANADIAN ENTOMOLOGIST. 227 



perceptible. Much attention has always been given to the fatalities affect- 

 ing this group, on account of the long series of specimens desired, so that 

 any causes frustrating this end have been regarded with apprehension, 

 and have been investigated as far as possible. (See Can. Ent., Vol. 

 XXX., 126.) 



In studying larval conditions, the close relationship existing between 

 the species makes attention to minor details of structure necessary- 

 Applying a general description to these larvae, we would note their bodies 

 being very cylindrical and provided with sixteen legs. The head is mod- 

 erate in size, well rounded, slightly bulging, with clypeus evident ; is 

 usually a shining brown, and marked laterally with a black, somewhat 

 oblique, line or dash. Mouth-parts are strong and compact. The 

 thoracic shield is a conspicuous feature, often as wide as the head, and, in 

 being a hard corneous plate, offers the protection needed here in a boring 

 insect. The anal plate is also large, and defends this extremity. The 

 various setpe arising from the tubercles and borders of the plates are ex- 

 ceedingly weak, and scarcely discernible except by using a lens. From 

 being so minute, arid not quite assured of their constancy, particular 

 reference to them does not seem important. 



In the matter of coloration, all agree in their earlier stages in having 

 whitish dorsal, subdorsal and partial substigmatal lines contrastingly 

 drawn on a dark brown or purplish body colour. These lines become 

 less distinct at each subsequent moulting, and are lost, or nearly so, at 

 maturity, when the colour becomes an undecided translucence of a 

 slightly varying hue, which is affected somewhat by the kind of food plant 

 eaten. With most species there is an abrupt termination to the lines, ex- 

 cepting usually the dorsal, on the first four abdomidal segments, and 

 sometimes on the last thoracic segment also. This gives an appearance 

 at once noticeable, but only occurs up to the next to final change, when 

 any contrasting colour effects are generally lost. For illustration see 

 Can. Ent., Vol. XXIX., pi. 6, where purpurifascia is shown in next to 

 last stage. 



For comparison of tubercle arrangement, these creatures form ideal 

 subjects. These latter are large, corneous, often shining black, and 

 always strongly defined. On thoracic joints two and three, I. a, I. b and 

 II. a are small ; II. b, III. and IV. are very large, the most conspicuous 

 of any of the lateral ones, and are situated in the form of an equilateral 



