AQUATIC MIDGES AND SOME RELATED INSECTS. 31 



halteres yellow; metanotum and sternopleura buff colored. Wings white, longitudinal 

 veins and cross veins not infuscated. Cubitus forking distinctly beyond the cross vein; 

 third and fourth veins ending about equally distant from the apex of the wing. Abdomen 

 light green, densely clothed with long yellow hairs. Segments without distinct fascia. 

 Hypopygium as in figure 17. Legs whitish, fore tarsus not bearded, second and third 

 joints densely bearded for their entire length. Tibial comb darkened on all legs; basal 

 segments of fore tarsus more than one-half longer than the tibia, proportions as 47 : 30. 

 Pulvilli well developed, empodium, narrow. Length, 4 millimeters. 



Female. — Antennae yellow, apical joint slightly infuscated, seven jointed; posterior 

 margins of the abdominal segments with a narrow whitish fascia. Otherwise like the 

 male. Length, 3.5 to 4 millimeters. 



Group V. — Trichocladius nitidellus Malloch. 



To this group belong those larvae which feed directly and apparently by preference 

 on filaments of Spirogyra. Trichocladius nitidellus Malloch, a species described in 1915, is 

 the only species that the author has thus far found which properly belongs here, although 

 Lyonet (1832) described the habits of a species which obviously belongs to this group. 

 Miall and Hammond (1900) state that this species has been rediscovered and studied 

 by T. H. Taylor. They give in considerable detail the habits and behavior of this larva 

 based on Taylor's observations. But it seems to the writer that there is a considerable 

 difference between the two species and that the larva studied by Taylor agrees more nearly 

 with that of Trichocladius nitidellus, which the author has studied, than with that ob- 

 served by Lyonet. This difference will be more readily understood after the feeding 

 habits of Trichocladius have been outlined. 



FEEDING HABITS. 



The description of the habits of this group has been well given by Miall and Ham- 

 mond (1900, p. 11-17) based on Taylor's studies. Trichocladius nitidellus differs only 

 in a few details. Filaments of Spirogyra are eaten exclusively by the older larvae. There 

 seems to be some selective ability exercised in the choice of filaments when more than 

 one species of Spirogyra is present. This selection favors the smaller filaments. The 

 larva often seizes a filament near the middle and forces the loop down its throat two 

 fibers abreast. The same thing is often done with the larger filaments, and only occa- 

 sionally are they bitten off completely. In this respect the author's observations differ 

 from those of Taylor, who says: "A filament of Spirogyra is seized by the mandibles and 

 bitten in two." 



Taylor also states: "The labram beginning at one end of the filament draws it into 

 the gullet by a stroking action." The labruin is not so well adapted to meet the require- 

 ments of this method of feeding as the lateral arms which are located on the epipharynx. 

 This will become more obvious when it is understood that the filaments are only crushed 

 a little between the mandibles and possibly also between the labrum and the labium. 

 This leaves the filaments in so natural a condition that when evacuated they immediately 

 straighten out into their original shape. The stroking action of the labrum on a smooth 

 filament, it would seem, is a far less effective method of forcing such a filament down 

 into the stomach than the contact on either side by a well-developed pair of lateral arms 



