244 The Ohio Naturalist. [Vol. 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, O.IS 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 min. 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 Universitv were partiallv filled with sedi- 

 ment and water plants of various kinds and set aside to wait the 

 development of Protozoa and H^'dra 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 l)lack aphids 

 which were apparently as much at home on the water as any 

 other ])lace. 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 



