138 
Psyche 
[December 
BIOLOGY OF THE TACHINID WINTHEM1A 
DATANJE TNS. 
By Frank L. Marsh 
Union College, Lincoln, Nebraska 
In a recent study of the parasites of Cecropia in the 
Chicago area based on the examination of over three thou- 
sand Cecropian cocoons collected in that region 1 some inter- 
esting facts were discovered in the life-history of the tachina 
fly Winthemia datanae Tns. For the identification of this 
insect the writer is indebted to Mr. J. M. Aldrich of the U. S. 
National Museum. In this instance every case of tachinid 
parasitization appeared to be the work of this single species. 
Over the entire area at least three percent of the mature 
Cecropian larvae were destroyed by this insect. 
Emergence , Breeding Habits , and Oviposition 
During a normal season the first adults emerge the second 
week in July. This appearance happens to be well timed 
because at that juncture the earliest of the Cecropian larvae 
have molted the last time before spinning their cocoons. 
When considered over the whole area the parasitization is 
rather light but it is the habit of this tachinid to work in 
limited spots probably including a half dozen trees. In 
these sporadic areas the infestation is heavy often amounting 
to the total destruction of the host larvae. Where taller trees 
were infested by Cecropia six times as many of its cocoons 
were parasitized by this tachinid when spun below the 
fifteen-foot level as when spun above that level. 
Copulation and egg-laying occur rather intermittently. 
The males rest on the leaves of the infected trees, at times 
engaging the females during temporary cessation of their 
a Marsh, F. L. 1934. “A Regional Study of Samia cecropia and Nine 
Associated Parasites and Hyperparasites.” An unpublished Master’s 
Thesis in the Northwestern University Library, Evanston, Illinois. 
