1941] 
Habits of Eucharidae 
67 
clearly indicated. These larvse do not possess the posterior 
spiracles ; in fact the presence of spiracles is not mentioned 
in the descriptions, and the occurrence of an open tracheal 
system in the planidia of this family is still debatable. The 
small size of the planidia would permit of cutaneous respira- 
tion, and sufficient air may possibly enter the opening of the 
funnel and surround the body to provide for their needs. 
Eighteen planidia of Orasema sixaolx and seven of 0. 
costaricensis were found in the bodies of Solenopsis and 
Pheidole larvse and none was found externally upon either 
larvse or pupse. The intermediate instars were not found 
but the mature larvse of 0 . costaricensis occurred free in 
the nest. It is therefore not known whether the larvse are 
endo- or ectoparasitic after the first molt. 
The ectoparasitic manner of development of Orasema 
had been conclusively demonstrated by W. M. Wheeler in 
his early work (1907) upon O. wheeleri Wheelerl and others 
in Texas and Colorado, and later authors found the same 
habit in other genera. It was consequently believed that the 
habit was general in the family. It was doubly unexpected 
that the endophagous habit should appear in species which 
belong to this same genus and are parasitic upon the same 
genera of hosts. 
Another feature in the biology of the two species of Ora- 
sema above mentioned is that they appear to be strictly 
larval parasites, whereas other species of the family are 
known to complete their development only on the prepupa 
or pupa. The endophagous habit may be associated with 
the change in the host stage which is attacked. Somewhat 
similar differences in developmental habits are known in 
the related Perilampidse. 
The Life Cycle 
The complete life cycle, with the duration of the different 
developmental stages, has been determined only for Stilbula 
tenuicornis. This species passes the winter and a large por- 
tion of the following season, representing an elapsed time 
1 According to A. B. Gahan (U. S. Natl. Mus. Proc. 88: 425-458, 
1940) the biological data presented by Wheeler under Orasema viridis 
Ashm. relate to O. wheeleri instead. 
