18 THE NORTH AMERICAN SPECIES OF DROSOPHILA. 
Hymenopterous parasites: The young stages of Drosophila are 
parasitized by various species of Hymenoptera. Ashmead has de- 
scribed a few species, Martelli (1910) has given an account of others, 
and I have bred afew. Perkins (1913) states that he has bred at least 
five species of parasitic Hymenoptera (belonging to the proctotrupoid, 
cynipoid, and chalcidoid groups) from the larve of Hawaiian Droso- 
philine. I am inclined to think, however, that these forms are not 
very serious enemies. They do not often emerge from exposed fruit 
that contains Drosophila larve and pupe. 
Predacious enemies: Fermenting fruit frequently contains predacious 
beetle larve (Staphylinide and apparently Nitidulide), that must 
destroy many Drosophila larve. I think these are probably the most 
serious natural enemies of Drosophiline. 
I have seen domestic fowls scratching apart fleshy fungi and eating 
the larve contained therein. These larve were chiefly Phoride, but 
some of them were Drosophilinze (Leucophenga and Mycodrosophila). 
Adults are preyed upon by spiders and by flies of the empidid, 
cordylurine, and anthomyiine groups. I have seen an empidid, 
Elaphropeza flavida Williston, destroy many Drosophiline in ‘Cuba, 
where the species is common. 
Perkins (1918) states that, in Hawaii, a crabronid wasp often fills 
its cells with a species of Drosophila. 
VI. ANATOMY. 
The following account of the structure of the various stages has 
been made sufficiently general to apply to all the members of the 
genus Drosophila known to me, and usually to the other members of 
the subfamily also, unless otherwise stated. In most cases the points 
have been worked out first with D. melanogaster, D. funebris, or D. 
immigrans, and then checked up by an examination of other species. 
Throughout the preparation of this part of the paper I have had on 
hand living stocks of about 15 species belonging to the genera Dro- 
sophila, Chymomyza, and Scaptomyza, as well as slides of larve and 
cleared specimens of numerous other forms. Many of the points 
have been checked by examination of pinned material of the rarer 
species. 
EGGS. 
The eggs of several species of Drosophiline are shown in plate 1. 
Those of Drosophila melanogaster are about 0.6 mm. long, those of 
Chymomyza procnemis about 0.5 mm. All the species in which I have 
investigated the matter have white eggs, with a fine meshwork of 
raised lines (not shown in the figures) over their surfaces. These are 
apparently the remains of the follicle cells that secreted the chitinous 
ege-shell. The filaments at the anterior end are present in all the 
