SEXUAL CHARACTERISTICS OF THELIA 547 
Thelia lays its eggs in late September and in October. At 
this time the males are already becoming lessnumerous. The 
female lays her eggs in the bark of the small branches of Robinia. 
I have never seen eggs being deposited at the bases of trees as 
described by Funkhouser (’15), who has written a very good 
account of the life history of Thelia and has described the five 
instars. With her sword-like ovipositor the female makes a slit 
through the bark, longitudinal to the branch and tangential to 
the underlying wood part. The total length of the egg is 2.4 
mm. The chorion forms a tube 0.4 mm. beyond the contained 
ovum, which is, therefore, but 2 mm. in length. This chorionic 
tube projects from the slit in the bark and probably aids in the 
respiratory changes of the developing embryo. From three 
to sIx eggs are deposited in a single slit and one Thelia will lay 
between thirty and forty eggs at a time, judging from dissections 
of adults previous to laying. The eggs remain in the bark over 
winter. In early June they hatch, and the small shiny brown 
nymphs begin to feed out on the small branches of the tree. 
They occur in cracks in the bark at the bases of thorns, or at the 
edges of healed wounds where the bark is thin and succulent. 
First, second, and third instars occur on the branches, constantly 
attended by ants. Soon, however, the ants begin to build the 
collars at the bases of the trees and third to fifth instars are found 
in abundance only inside these collars. As described above, 
they emerge as full-grown nymphs in July, crawl higher on the 
tree and molt into adults. 
5. APHELOPUS THELIAE (GAHAN), A POLYEMBRYONIC PARASITIC 
DRYINID; ITS LIFE HISTORY AND HABITS 
The life history and habits of Aphelopus theliae were gradu- 
ally worked out by the author until at the present time we have 
a fairly complete story. The difficulty in getting the series of 
events in the life cycle complete was due to the fact that until 
the past summer (1917) the stay at Cold Spring Harbor had not 
begun early enough in June to obtain adults and to see the lay- 
ing of the Aphelopus egg in the nymphs of Thelia. 
JOURNAL OF MORPHOLOGY, VOL. 32, NO. 3 
