1937 ] 
The Tachinid Winthemia datanae 
139 
egg-laying activities. During oviposition the female hovers 
over the back of the larva, clinging to its tubercles while the 
eggs are securely attached by their adhesive coating to the 
skin of the host along the dorsal line. The largest number 
observed on one larva was 76 while the average was 21. In 
every case observed larvae in the earlier stages were passed 
by, eggs being placed only on those which had molted the last 
time before spinning. Because of this adaptive behavior the 
eggs are not shed with the larval skin at molting time. The 
host larvae give little heed to the egg-laying, only temporarily 
stopping their feeding. Oviposition occured more commonly 
in the latter part of the afternoon on the shaded side of trees 
and bushes. 
Egg and Larva 
The eggs are white and measure about 0.8 mm. x 0.3 mm. 
In about thirty-six hours the endophagous larva gnaws an 
opening near one end on the adhering side of the egg and 
tunnels down directly into the coelomic fluid of its host. 
Bacterial action causes a blackening of the area of the cuticle 
where the tunneling occurs and a characteristic dried patch 
appears around the egg shells in a few hours. 
The larvae develop rapidly but due to the eggs having been 
laid on mature larvae the host almost invariably completes at 
least the outer shell of its cocoon before being killed. Such 
cocoons are usually white in color. If few tachinid larvae 
are present the cocoon may be fully completed before the 
host larva is killed. In every case observed the infected 
larva always died although it may have been parasitized by 
but a single tachinid larva. In instances of heavy infestation 
death of the host occurs in three or four days after the 
parasites emerge from the eggs. 
The dead host turns brown in color and usually presents 
a distended appearance. Oxygen seems very essential to 
adult tachinid larvae, evidenced by an opening which is in- 
variably made in the skin of the host, usually on the ventral 
surface. This same hole is later used as an exit from the 
tough, dried skin of the host. The larvae mature in from six 
to eight days and may crawl out immediately or may rest for 
a time in the dried host skin. If a cocoon containing adult 
