232 F. W. EDWARDS. 



larvae of S. reptans could be found. Since, however, the only structural difference 

 between this form and S. reptans is in the simple or less branched gills, it seems on 

 the whole most probable that it is a variety of reptans, and I have so regarded it 

 pending further investigation. The name has reference to the cap-like black patch 

 on the head of the larva, a most striking feature. 



6. S. morsitans, Edw. (figs. 1/, 4/). 



Adult. — Both sexes have now been obtained by breeding. The female is very 

 difficult to distinguish from that of venustum ; there seems to be no constant difference 

 in the colour of the base of the abdomen, as I previously thought, but this species 

 may perhaps be separated (in the female sex) by the greater amount of yellow on 

 the middle tibiae. The only clear distinction in the adult, however, appears to be in 

 the shape of the male claspers. 



Larva. — General colour rather pale yellowish-green without distinct darker 

 markings. Head yellowish, the clypeus with a conspicuous and rather sharply 

 defined black mark in the form of an H. Antennae 4:-jointed, the second joint a 

 little longer than the first, third scarcely as long as second, fourth minute. Mentum 

 with 9 teeth in the terminal row, the middle one long, the one at each end very 

 broad, intermediate ones indistinctly trilobed ; four or five long hairs at the sides. 

 Last abdominal segment without ventral papillae. Anal sucker with 65-70 rows 

 of hooks, about 15-20 in each row. Skin round anus bare. Gills with 5 or 6 branches 

 all approximately equal in size. 



Pupa. — Respiratory filaments 8, about as long as the pupa, in four pairs, the 

 two lower pairs slightly thinner than the upper, and arising from a short common 

 stalk ; each of the four pairs also with its own stalk, that of the lowest pair distinctly, 

 often much, longer than the others ; all the filaments in the vertical plane, not at 

 all swollen towards the base. Cocoon as in >S. ornatum. 



Habitat. — Weedy rivers of moderate current in company with S. ornatum, 

 S. venustum and other species. Not found as yet in small streams. 



Breeding season. — There may be two broods in the year, as adults have been 

 obtained in May and July, but the May brood is certainly the more numerous. 



Material collected. — Two males were reared from pupae found in the river Granta 

 at Hauxton, Camb., 5.vii.l5, on Scirpus in company with large numbers of 

 S. equinum and S. argyreatum. A fair number of larvae and pupae were found on 

 grass and Ranunculus at the edge of the Lymington River, near Brockenhurst 

 Bridge, New Forest, 2. v. 20. 



7. S. venustum, Say {austeni, Edw.) (figs. 1^, U). 



Adult female. — A number of females have been obtained by rearing ; they appear 

 to differ from those of S. morsitans as shown in the table. I have failed to discover 

 a better distinction. 



Larva. — General colour bright green, the abdomen with rather indistinct bands 

 of darker green. Head light in colour, with a pair of somewhat oval dark spots at 

 some distance from the neck, lying close together, connected at or near their anterior 

 ends by a transverse bar ; usually also a dark area along the posterior margin of the 

 clypeus. (The areas which in most species are dark are here pale, with dark areas 



