164 THE CANADIAN ENTOMOLOGIST. 



hatch and that the caterpillars can be easily reared, should appeal to 

 teachers of zoology and insect life, especially when it is considered how 

 readily the food-plant may be grown in the garden. 



Description. 

 Egg. — Echinoid in type ; firmly attached to the leaflet by a flattened 

 base, top flattened to a lesser extent, the centre being occupied by a 

 moderately deep pit, at the bottom of which is a very fine network. 

 Chalky-white when first laid, which colour is retained in those specimens 

 kept unmoistened indoors, but is changed to a brownish in those moistened 

 or exposed in the field. From this it would appear as if the change in 

 colour is due to staining from the juices of the leaflet rather than anything 

 inherent in the egg. The surface shows a raised network, the intersections 

 of which are enlarged into blunt, thickened knobs, while the ridges be- 

 tween are thinner and lower. Near the base of the egg the network is 

 finer, the spaces more numerous and the raised intersections less promin- 

 ent. Two eggs gave the following diameters : Vertical, 0.45 mm.; 

 equatorial, 0.7833 mm.; vertical, 0.46 mm.; equatorial, 0.7833 mm. 



First Instar. — On emergence the caterpillar is nearly cylindrical, 

 slightly broader in the thoracic region ; venter flat. As it grows the thorax 

 becomes highest at the third thoracic segment, sloping gradually caudad 

 and abruptly cephalad, and the first thoracic segment is now very large, 

 and at least twice the cephalo-caudal diameter of the succeeding segment; 

 between the sutures highly arched. 



Head small, rounded, dark brown, retractile ; at rest the thoracic 

 segments are swung forward around a transverse axis, so that the head 

 comes to lie directly underneath the first thoracic segment and is with, 

 drawn into it. 



Colour pale clay yellow or pale brown, but after feeding a few days 

 changing to pale green ; lateral and dorsal surfaces, except for a very 

 small central area on the dorsal surface of each segment, thickly studded 

 with minute black dots. 



Each half of the caterpillar bears six rows of prominent tubercles ; the 

 two dorsal and the substigmatal rows give rise to colourless bristles, while 

 the other three rows, dorso-lateral, lateral and sub-ventral, are without 

 bristles ; the tubercles are slightly elevated above the surface, on each 

 segment those of the inner dorsal row are placed cephalad of those in the 

 outer dorsal row, and are at least twice the height of the tubercles of both 

 the outer dorsal and substigmatal rows, which are very flat. 



