BIONOMICS AND DEVELOPMENT OF LYGOCERUS sp. 109 
a cone with the head projecting from the blunt end. The 
tracheal system is more complex: the ramifications of its 
branches are more numerous, and those of the second segment 
appear at this stage. The stigmatic trunks of segments six, 
TExtT-FIa. 5. 
Mouthparts of second stage larva. x 400. Ventral view. o0.sal.= 
aperture of salivary duct. sk,=endoskeleton of head. lab.= 
labium. m.lab.= muscles of labium. Jbr.=labrum. md. =man- 
dibles. sal. d. =salivary duct. 
seven, and eight are visible at the junction of the dorso- 
lateral branches with the main stem of the tracheae, but 
the corresponding spiracles are still closed. This stage lasts 
about thirty-six hours, and during this time the host dies and 
becomes black and shrunken. The hyperparasite seems to 
feed by suction, and the skin of the Aphidius, otherwise 
uninjured, is gradually emptied of its contents. As the fluid 
from the decomposing tissues passes into the mesenteron of 
the Proctotrypid, the latter changes in colour from yellow to 
brown. 
THIRD STAGE LARVA. 
Dimensions 1:00 x -75 mm. 
TEXT-FIG. 6. 
Larva of the third instar, showing tracheal system. x 49, 
In the third stage the body becomes globose, owing to the 
increased proportionate development of the first seven or eight 
segments to accommodate the distended mesenteron. The result 
