206 
BLACK AHCHES. 
more slender than in the preceding genera, the 
male having the apex of the abdomen slightly 
tufted, ■while that of the female is naked and atte- 
nuated*. Psilura is very closely related to Hvpo- 
gymna, a genus including the Gipsey Moth, whose 
curious economy renders it an object of much 
interest. Tlie principal differences consist in the 
relative length of the articulations of the palpi and 
the appearance of the abdomen in the respective 
females, that of the Gipsey Moth terminating in a 
dense tuft of hairs. 
The male of the Black Arches Moth generally 
expands from fifteen to eighteen lines, the female 
about two inches. Both sexes vary considerably, 
but the following description will apply to the ma- 
jority of specimens. The surface of the primary 
wings is greyish-white, with numerous black spots, 
and four confused zigzag transverse lines of the 
same colour. Several of the spots are placed at the 
base of the wing, one before the middle between 
the two anterior lines, and a regular series tdong 
the terminal border. The secondary wings are 
brownish-grey, sometimes white at the hinder extre- 
mity; the fiinge always white, spotted at regular 
intervals ivith black. The thorax is white, tinged 
with yellow in front, and marked with several 
black spots; the abdomen rose-red behind, >vith 
the incisures and series of spots black, that of the 
female terminating in a yeUow corneous oviduct. 
* The generic name refers to this circumstance, being 
derived from naked, and the tail. 
