Chernovskiia orbicus (Townes)

(Fig. 3)

Chernovskiia orbicus (Townes, 1945: 151).

Material examined. JAPAN: Gifu Prefecture, Hajima City, Kiso River, 32–34 km from mouth, 2 larvae, 1996, 1997, N.

Kitagawa (Kitagawa’s code 8210-1, 2).

Larva [Characteristics of C. macrocera according to Saether (1977) and Pinder and Reiss (1983) in brackets]. Head. Basal antennal segment about as long as 2nd and 3rd segments combined [basal segment shorter than 2nd segment]; antennal blade placed medially on 4th segment (Figs. 3A, B) [on 3rd segment]. Mandible (Fig. 3C) lacking inner teeth [with single, triangular inner tooth]. Premandible (Fig. 3E) with 3 teeth pointed apically, brush absent. Mentum (Fig. 3D) pale, anterior margin strongly concave [almost semi-circular], with broad, subrectangular [triangular] median tooth and 5 pairs of lateral teeth, the 2 outer pairs smaller than the remaining [the 2 outer pairs much larger than remaining teeth and curved inwards subapically]. Prementohypopharynx complex (Fig. 3F) with pair of long, cowhorn-like projections [not mentioned by Saether (1977) or Pinder and Reiss (1983)].

Body. Nine subdivided anterior segments (Fig. 3G). Anal tubules (Fig. 3H) long, slender. According to Pinder and Reiss (1983), the subdivision of the anterior segments is due to elongation of the intersegmental region and may be an artifact of the preservation.

Remarks. As mentioned in the description, the features of Kitagawa’s larvae coincide well with those of Chernovskiia orbicus (Townes, 1945) (see Saether 1977: 109, 111). Thus, even if no adults are available, it can be concluded that C. orbicus undoubtedly occur in Japan.