274 THE CANADIAN ENTOMOLOGIST 



36) has recorded 7 stages for the 9 larva of arge, spring brood; 

 we are practically certain that we have missed no stage in our 

 brood of michabo, so if the number of moults is constant, it would 

 form a further means of differentiation between the two species. 

 Of the two michabo would seem to be the newer species, 

 l)eing a further development of the arge type, as the subdorsal line 

 is present in the earlier stages only, being obsolescent or wanting 

 in the mature larva. 



Acronycta impressa Wlk. 



We use this name in the ordinarily accepted sense, i.e. for the 

 species as figured by Smith in his Monograph of the genus Acro- 

 nycta, PI. XIII, figs. 4 and 5, and of which verrilli G. & R. is re- 

 garded as a synonym. The type of impressa Walker in the British 

 Museum is in such poor condition that on a recent examination 

 we were unable to tell definitely to just what form the name should 

 be applied; until material from the type locality is available, more 

 or less doubt will surround the application of the name. We 

 receiyed ova of the species late in the fall of 1914 from New Washing- 

 ton, Pa.; the larvae fed up readily on poplar and pupated within a 

 month from the time of emergence from the egg. Two 9 's 

 emerged the same fall, the remainder of the pup^e hil)ernated 

 and produced imagines early the following spring. 



Ovum. — Rather flat, base of egg broad, irregularly circular, 

 about 1 mm. in diameter, with a slight rim around the periphery; 

 from this rib arise 50-60 ribs, arranged more or less in pairs, which 

 ascend the sides of the egg about half way to the micropylar area 

 where the two component parts of each pair join and are either 

 continued to the micropylar area by a single rib or else end blindly; 

 occasionally the upper ends of two pairs are joined by the single 

 rib. Colour when first laid yellow, becoming later purple with 

 numerous white blotches and finally almost black. 



Stage I. — Head shiny black; body white with abdominal 

 segments I, IV, V and VIII deep black-brown to below the spiracles: 

 traces of a dark dorsal stripe especially on segments preceding 

 and following the dark ones; on the white segments traces of a 

 lateral brown band situated above tubercle VI on a level with the 

 lower edge of the dark colour of the four above mentioned abdo- 



