Potassium Hydroxide hy Dicranura vinula. 405 
trivances to aid in rupturing tlie cocoon where this is 
necessary. 
Both D. furcula and D. bifida emerge from the 
cocoon, wearing a ^' shield similar to that formerly 
described in D. vinula. 
D. furcula. 
The pupal " shield is shown in Fig. 4 ; it is 
held securely on the head of the imago by hooks 
fitting into grooves and sockets situated just to the 
median side of each eye of the imago (Fig. 4, hk). 
In addition to these hooks^ there is also a pair of small 
processes projecting inwards from the inner ventral 
corner of the pupal eye (Fig. 4>, hh'). I could not 
find any definite socket for the reception of these, but 
there is on the ventral surface of each side of the head 
of the imago a triangular depressed shallow area, in 
which this pair of hooks must lie while the " shield 
is in position (Fig. 6, hh'g). After emergence the 
shield is removed by the tarsi of the front pair of 
legs, exactly as in D. vinula. 
The labral prongs present in D. vinula are here 
represented only by short blunt knobs (Fig. 5, I p), and 
can be of no service in piercing the cocoon. I believe, 
however, that the maxillary palps are brought to bear 
upon the softened surface. These appendages are pro- 
vided with far fewer and shorter hairs than in D. vinulay 
and are relatively stouter and harder ; their distal 
extremities are entirely devoid of hair, sharply pointed, 
and marked with transverse ridges like a miniature 
file (Fig. 6, p). The structure of these palps appears to 
vary as to the number of joints. In three specimens 
both palps were single-jointed ; in one specimen the 
right palp bore traces of three joints, but the left was 
single-jointed, while in another specimen both palps 
were distinctly three-jointed. The length of the palps is 
almost the same, viz., about 0*36 mm., whether single or 
three-jointed, and I am thus inclined to believe that 
a single-jointed condition is in process of evolution 
from the more primitive condition of three joints. 
Certainly the absence of intermediate articulations would 
render the palp a more rigid and efficient boring tool. 
