TRIFID^. 275 



scaled ; collar and shoulder lappets a little raised ; no real crest 

 at the back, though the long thoracic scales are drawn together 

 into a faint knob ; abdomen rather long, white, covered with 

 long white scales which rise in ridges not amounting to crests, 

 on the back of several of the segments ; lateral and anal 

 tufts dense and spreading. Fore wings rather narrow and 

 pointed ; costa gently curved to the apex, which is sharply 

 angulated ; hind margin slightly hollowed below it, then 

 obliquely and gracefully rounded off to the dorsal margin, 

 which is also curved. Colour whitish, abundantly dusted 

 with pale brown or pale reddish scales, and with longitudinal 

 faintly brownish stripes, occupying the spaces between the 

 nervures ; a slender dark-brown or blackish longitudinal line, 

 from the middle of the base, extends in a faint curve beyond 

 the middle of the dorsal portion of the wing and sometimes 

 nearly attains the hind margin ; another of a paler brown, ' 

 above it, lies along the upper side of the median nervure, 

 through the middle of the wing ; these two streaks being the 

 only conspicuous markings. Cilia white with a faint brownish 

 dividing line. Hind wings pure clear white ; cilia similar. 

 Female much stouter and with the fore wings more pointed 

 and frequently longer ; otherwise similar. Underside white, 

 faintly dusted with yellowish atoms along the costal margins 

 of all the wings ; fore wings with a row of slender black 

 dashes at the base of the cilia ; body white ; legs brownish, 

 browner in front. 



Slightly variable in the degree of reddish, or brownish 

 tinge on the fore wings and more so in the length and 

 intensity of the dark longitudinal lines. 



On the wing in June. 



Larva nearly cylindrical but flattened beneath ; rather 

 thickly covered with very soft short hairs ; head rather large, 

 rounded, black, with a large white triangle on the face, and 

 a pair of converging white lines above it ; body pale yellowish 

 dusted with black, with a broad black dorsal line, sometimes 



