THE GENUS ACRONYCTA AND ITS ALLIES. 
251 
completely as alni has. When ready to pupate, the larva will 
bore into rotten wood, or go into a stem of reed or elder, or 
will, like psi and tridens, form a cocoon on or under the surface 
in sawdust or loose rubbish. In rotten wood, which seems to 
please it best, it prefers, like alni, to go in horizontally in a 
perpendicular face, and then bore upwards ; but it differs 
altogether from alni, in that when it has closed the opening, 
to appearance in much the same way, the diaphragm so made 
is the actual top (or outlet) of the cocoon proper, there being 
no inner structure. The space excavated measures 14 mm. by 
5 mm., and is lined with a little silk, and here and there by a 
few chips removed apparently in giving a proper shape to the 
cavity. The thin silk operculum coated with chips, which forms 
the outlet of the cocoon, often shows no indication of the exit 
of the moth. The sides of the opening made, which is an 
irregular slit, falling together again. 
The pupa (PL III., fig. 3) is 13 mm. in length, wings 8, 
abdomen 5, width little over 3 mm. Pale greenish-brown, 
with a darker dorsal line, the leg and wing cases so trans- 
parent that the incisions of the segments within are very 
distinct, and the tracheal vessels running down the antennae, 
legs, etc., are obvious. The whole pupa looks extremely 
delicate and fragile. The outlines of the fat masses are 
visible through the abdominal walls. The spiracles are dark 
raised rings, and are the only solid looking parts of the 
pupa, there are two bristles in front between the eyes, the pair 
at the bases of the antennae are also distinct ; the sculpturing is 
extremely fine, and only distinct along the anterior margins of 
the abdominal segments as very minute close pitting. The 
anal armature consists of two dorsal and six ventral spines. 
These are long compared with the size of the pupa. The 
ventral set are regularly disposed at equal distances, the outer 
ones set at an angle of 45° ; all are hooked downwards. The 
amount of corrugated base is very small, but from the spreading 
of the spines they get well entangled with the silk of the 
cocoon, at the base of the spines there is a sloping area of 
longitudinal wrinkle^ beneath there is a transverse ridge at the 
base of the spines bounding some fine radiating ridges. The 
hooks at end of the spines form more than a semi-circle. 
{To be continued 1 ) 
