From the foregoing brief descriptions it is clear that the larva of Trichomyia urbica stands apart from other psychodid larvae not only in its mode of life, as a wood-borer, but also in its morphology. The regularly cylindrical body, devoid of dorsal plaques and long setae and the densely chitinized head give it a very different appearance from that of other psychodid larvae.

The small and heavily chitinized antennae are very different from those found in larvae of Phlebotomus, in which they are 3-segmented; Psychodes, in which they are delicate and dome-like; Sycorax, in which they are long and 4-segmented (Feuerborn, 1933); and Maruina, in which they are formed of small rods (Feuerborn, 1933).

The massive toothed mandibles, devoid of sensory processes, differ greatly from those of other genera of psychodids except Phlebotomus. Maruina, Sycorax (see Feuerborn, 1933), and Psychodes all have mandibles with large leaf-like processes and many long plumose or pectinate setae and sensory hairs or processes.

The maxillae, in all the three genera examined above, are delicate plates with ill-defined areas representing the maxillary palps, and with many delicate teeth, long setae and sensory processes arising from the body of the maxilla.

The lower lip in Trichomyia is very simple and the mentum is hardly distinguishable. In this respect it resembles Psychodes where the mentum is a simple transverse plate, and Maruina (see Feuerborn, 1933) in which it is similar except that the anterior border of the plate is fringed with long setae. In Phlebotomus the mentum is a densely chitinized plate with strong teeth on its anterior margin.

The anterior spiracles appear to be much alike in all the genera in which they are present; but in the position of the posterior spiracles Trichomyia, in which they are placed far back on the dorso-lateral region of the last segment, differs from all other genera examined except Phlebotomus, in which they occupy a similar position.

Therefore, as regards the shape of the body, nature of the cuticle, absence of long setae and of dorsal plaques, and the structure of the antennae and labrum, the larva of Trichomyia differs from all other psychodid larvae. It shares with the larva of Phlebotomus the possession of strong, simple, toothed, mandibles devoid of long setae and sensory processes. It also resembles Phlebotomus in the poorly defined epipharynx and premandibles on the labrum, and in the position of the posterior spiracles near the middle of the last segment. The weakly developed mentum of Trichomyia larvae, however, differs greatly from that of Phlebotomus larvae in which the mentum is very strongly developed as a toothed plate.