110 MAUD D. HAVILAND 
of this distension is to bend the head round ventrally to form an 
acute angle with the long axis of the body. The papillae on the 
head disappear. The branching of the tracheal system is more 
elaborate, and the spiracles of segments six, seven, and eight 
open in the order named, while the stigmatic trunk of the 
second segment appears. This stage is longer than the two 
preceding, and lasts about forty hours. The parasite is bathed 
in the fluid that oozes from the decomposing body of the host. 
Fourtu Stace LARVA. 
The larva in the fourth instar differs considerably from that of 
the preceding stages in size and form. Immediately after 
ecdysis, the dimensions are not much greater than those of the 
third instar, and the body is transparent; but as the larva 
ingests the remainder of its host, it grows rapidly, and when 
fully fed, measures 1-67 x 88 mm. At the same time it be- 
comes creamy white and opaque. 
The first four body segments are greatly developed. The small 
head is bent completely round to the ventral side, and is almost 
hidden by the large prothorax. The abdominal segments 
diminish in diameter posteriorly, and the last bears dorsally a 
conical caudal appendage. The function of this is unknown, 
unless it is used as a lever by the larva which is able to turn 
round freely in the cocoon. Seurat (26, p. 99) has described 
a somewhat similar appendage in a Chaleid, Enceyrtus sp., 
and supposes that its purpose is locomotion (fig. 9, cd.). 
Both the caudal appendage and body bear short chitinous 
papillae or spines. The head is without larval antennae or palpi. 
The mouth, which is very small and transversely oval,is bounded 
anteriorly by a large horseshoe-shaped labrum, and posteriorly 
by a smaller square labium. Between these, and deeply set 
within the buccal cavity, are two stout little mandibles (fig. 8). 
The salivary glands extend from the dorsal part of the fourth 
segment forwards on either side of the mid-gut as two straight 
tubes with a considerable lumen. They are formed of poly- 
hedral cells with large nuclei and granular cytoplasm, which 
stains deeply with haematoxylin. Each gland runs obliquely 
