CUSPIDATES. 



213 



cterior to the band is a small circular dis- 

 coidal spot, and again beyond this are certain 

 zigzag blackish lines, the outer of which 

 expands into a large transverse dark gray 

 blotch on the costa ; on the margin itself is 



series of eight small circular black spots : 

 hind wings of the male are white, with 

 an occasional smoke-coloured cloud and a 

 marginal series of black dots ; in both sexes, 

 but particularly the female, they have occa- 

 sionally a broadish smoke-coloured hind-mar- 

 ginal band, terminating in a diffuse spot 

 at the anal angle. The head and collar are 

 white ; the thorax whitish, varied with smoky 

 black ; the body gray, with smoke-coloured 

 bands. 



The EGGS are laid separately on the upper sur- 

 face of the leaves of aspen (Populm tremula), 

 the female selecting those dwarf shrubby 

 plants which grow in woods ; and in gardens 

 on the leaves of tacamahac (Populus balsami- 

 fera), about the 1st of July, and the young 

 CATERPILLAR emerges about the 14th ; it appears 

 to be full-grown about the 26th. It spins a silky 

 coating near the middle of the leaf of its food- 

 . plant, and, attaching itself to this, both by its 

 feet and claspers, it is very difficult to remove ; 

 it remains perfectly without motion during the 

 day exposed to the rays of the sun, and feeds 

 during the night. After feeding it sometimes 

 remains clasping the margin of the leaf it has 

 been eating ; when at rest the head is nearly 

 withdrawn into the second segment. The 

 eleventh, twelfth, and thirteenth segments 

 are elevated, and the anal horns are closely 

 approximate and pointing in a straight line 

 backwards ; the head is prone, and narrower 

 than the second segment into which it is 

 received ; the body rises from the head to 

 the fourth segment, which is produced into a 

 transverse dorsal ridge, whence the body gradu- 

 ally tapers to the anal extremity, the eleventh, 

 twelfth, and thirteenth segments forming a 

 cone ; at the anal extremity are two cylin- 

 drical tubes, each of which is covered with 

 short bristles, which give it a scabrous feel as 

 well as appearance ; and each of which also 

 contains a slender filament capable of being 

 protruded at the will of the caterpillar. The 



colour of the head is grayish brown, the sides 

 dark brown, the face delicately reticulated ; the 

 dorsal area of the body is gray-brown, marbled 

 with darker and lighter shades, and bordered 

 throughout with bright yellow : the lateral 

 and ventral areas are bright apple-green, 

 dotted with purple-brown, and every dot 

 emitting a small black bristle. On the fifth 

 segment the green colour extends completely 

 round the caterpillar, interrupting the dorsal 

 brown area, which recommences in a point, and 

 increases in breadth to the eighth segment, 

 on which it descends below the spiracle ; it 

 then gradually narrows to the twelfth segment, 

 and again expands on the thirteenth. The anal 

 tubes are green, with a brown patch on the 

 inner side of each near the base ; they have a 

 brown ring beyond the middle, and a second 

 paler ring at the tip ; the filaments are black, 

 the spiracles brown ; the ventral surface of 

 the segments is blotched with brown ; the 

 legs are green, each joint having a red mark 

 on the outside. When full-fed this caterpillar 

 excavates a portion of the bark of the tree on 

 which it feeds, and in this constructs a very 

 strong glutinous cocoon, so like the bark in 

 colour as to be seen with difficulty. 



The MOTH appears on the wing in June, and 

 is very widely distributed in England ; and 

 Mr. Birchall says it is not uncommon and is 

 widely distributed in Ireland. (The scientific 

 name is Dicranura bifida, and this name also 

 includes Cerura arcuata and C. fuscinula of 

 Stephens.) 



Obs. Notwithstanding the perfect convic- 

 tion I feel that Dicranura furcida and D. 

 lifida are distinct species, I am bound 

 to acknowledge my inability to make the 

 difference apparent in words. The exterior 

 margin of the median band in D. furcula is 

 generally more concave or scooped out below 

 the costa than in D. bifida ; the median band is 

 darker- coloured in bifida, it is more inclined 

 to orange in furcula ; bifida is also a larger 

 insect ; but these are comparative differences 

 only, and therefore we must appeal to the 

 differences in food and colour of the cater- 

 pillars, when all doubt of the distinctness of 

 the species will be at once removed. 





