244 
The Ohio Naturalist. 
LVol. VIII, No. 3, 
IV which is imbricated, both being without sensories; V nearly 
as long as IV with one sensory near distal end; VI ('including 
unguis'! nearly as long as III, IV and V taken together, deeply 
imbricated. At the base of the unguis is a group of six or seven 
sensories as in the winged form. Total length of antennae 
1.15 mm.; length of I, 0.06 mm.; II, 0.07 mm.; Ill, 0.22 mm.; 
IV, 0.18 mm.; V, 0.16 mm.; VI, 0.10 mm.; VII, 0.38 mm. Beak 
stout reaching third coxa. Thorax narrow, the pro-thorax bear¬ 
ing a lateral tubercle. On the sides of the thorax below the 
tubercle are three pairs of very distinct wax glands secreting a 
white flocculent material which covers the side and ventral por¬ 
tion of the thorax. Legs long and slender; tibia provided with 
four more or less regular rows of long hairs. Legs with the 
exception of the tarsus covered with a fine pulverulence. Abdo¬ 
men large and swollen, the second and eighth abdominal seg¬ 
ments with distinct lateral tubercles and bristles which project 
out above them. Honey-tubes slightly vase-shaped, 0.35 mm. 
long. Cauda 0.10 mm. long, which with the anal plate resemble 
the same structures in the winged form. Color, dark brownish 
or greenish black, but becoming a clear green under poor food 
conditions. Frequently forms will be found with three longi¬ 
tudinal black stripes down the abdomen. Older specimens may 
be nearly jet black in color. Total length of body, 2.10 mm.; 
width of abdomen 1.15 mm. Immature resembling adult but 
frequently lighter in color. 
The circumstances which led to a special study of this form 
are as follows: 
During the latter part of last September a number of aqua¬ 
ria at Ohio State University were partially filled with sedi¬ 
ment and water plants of various kinds and set aside to wait the 
development of Protozoa and Hydra for class use. One large 
aquarium containing Philotria canadensis was placed just outside 
the window where it remained for some time until a thick growth 
of the Philotria developed, the tips of which projected slightly 
above the surface of the water. 
On October 14 the aquarium was brought into the laboratory 
and great was my surprise to find the surface of the water and 
tips of the projecting Philotria covered with small black aphids 
which were apparentlv as much at home on the water as any 
other place. A careful search was made for a winged form which 
might have started the colony but none could be discovered. 
The only individuals present were dark brownish-black apterous 
females. At first I was led to believe that the presence of aphids 
on so strictly an aquatic plant as Philotria was purely accidental 
and that some chance migrant from an annual plant had fallen 
into the aquarium and having the ability to adapt itself to the 
new food plant at once began to reproduce. The off-spring 
