Potassium Hydroxide by Dicranura vimila. 407 
of the flask-shaped cocoon^ and thus the labour imposed 
upon the moth is lessened. Judging only by the size 
of blue stain produced, the amount discharged is little 
less than that produced by D. vinula. The head of the 
moth and of the pupa present no modifications corre- 
lated with the possession of a hard cocoon. 
Bomhyx callunsej B. lanestris, and Limacodes testudo. 
These three species form a group by themselves, 
inasmuch as their cocoons have many points in common, 
and all three have similar appliances for escaping. The 
cocoons are all tough, more or less cylindrical with 
rounded ends, one of which is raised as a lid at the 
time of emergence. The boring organ is of a totally 
different kind to that existing in the Dicranurans, and 
is not formed either by labral prongs or modified 
maxillary palps, nor does the anterior portion of the 
pupa form a " shield to the head and eyes of the 
imago. On the contrary, by carefully denuding the 
head by brushing and blowing, it may be seen that the 
head is far more turned down, so as to bring the mouth 
parts into a more backward position, while the median 
frontal portion of the head between the eyes is pro- 
duced forward into a prominent and sharply-pointed 
umbo or boss (Fig. 9, h) of great strength, and capable 
of being used as a powerful awl in opening the lid of 
the cocoon. There are slight differences in the details 
observable in the three species named. B. callunse 
and B. lanestris have the boss developed to a less 
degree and less sharply-pointed on the head of the pupa 
also (Fig. 8), while in L. testudo the converse holds 
good, the boss being far sharper and stronger in the 
pupa than in the imago (Figs. 10-12). Indeed, the pupal 
boss is the only hard structure on the otherwise fragile 
and delicate pupa case of this species. I am inclined 
to think that the lid of the cocoon is broken open before 
the imago of L. testudo has got free from the pupa case. 
I was unable to make any direct observations on this 
point, since the larva does not pupate till many weeks 
after the formation of the cocoon, the whole winter and 
early spring, in fact, being passed in the larval condi- 
tion j and, further, the species is, in my experience, 
