234 F. W. EDWARDS. 



8. S. tuberosum, Lundstr. (fig. ij). 



Larva. — General colour dingy greyish or greenish grey ; head pale above, without 

 dark markings ; abdomen with dark dorsal bands on the first five segments, the first 

 two sometimes interrupted ; segments 6-8 all dark above. Antennae as in S. reptans. 

 Mentum with 9 teeth in the terminal row, all simple, the middle one and the one at 

 each end considerably larger than the others. Anal sucker with about 80 rows, 

 each containing 12-15 hooks. Skin round anus bare. No ventral papillae on 

 last segment. Gills each with from 6 to 8 branches. 



Pupa. — Respiratory filaments 6, in three pairs, each pair distinctly stalked ; 

 filaments much longer than the pupa and all directed nearly straight forwards ; 

 the two ventral pairs appear to be given off from the main stem which terminates 

 in the dorsal pair. Cocoon constructed as in S. ornatum, but smaller, both actually 

 and relatively to the pupa, rarely extending beyond the middle of the thorax. 



Habitat. — With S. reptans. 



Breeding Season. — As in S. reptans. 



Material collected. — The species was very numerous in Machrie Water and 

 Brodick Wood Burn, Arran, v-vi.l919, in the latter much more abundant than 

 S. reptans, though in the former S. reptans predominated to some extent. Also 

 found in Devonshire, in small numbers in the river Dart at Holne Chase, and the 

 river Teign below Fingle Bridge. The occurrence of this species and of S. reptans 

 so far south is of interest, and was somewhat unexpected, but their association 

 with hilly country is confirmed. 



Variation. — None noticed, except to a slight extent in the size of the cocoon. 



Bloodsucking. — No further data available. 



9. S. argyreatum, (Mg.) Lundstr. (figs. Ih, ik). 



Larva. — General colour rather reddish grey. Back of head with four distinct 

 rather elongate dark spots, the posterior one darker than the others, usually all 

 enclosed in a dark cloud ; dark eyebrow present, but without any included darker 

 dot. Abdomen with a conspicuous dark band on each segment. Antennae as in 

 S. reptans. Mentum with 11 teeth in the terminal row, the middle one and the 

 second from each end somewhat larger than the others. Anal sucker with about 

 80 rows, each containing 14-18 hooks. Skin round anus with a very few simple 

 scales. Very small ventral papillae on last segment. Gills simple. 



Pupa.- — Respiratory filaments 6, about as long as the pupa, not arranged definitely 

 in pairs, but all arising almost from a common base and spreading out considerably 

 at the base in all directions ; the uppermost one a little thicker than the other five, 

 its basal part approaching the vertical. Cocoon as in S. ornatum. 



Habitat. — Weedy rivers with only a moderate current, usually associated with 

 >S. ornatum or S. equinum or with both these species. The larvae and pupae seem 

 particularly fond of the leaves and stems of Scirpus lacustris, and of other plants 

 with ribbon-Hke leaves, though they are by no means confined to these plants. 

 The larvae predominate on the lower sides, the pupae on the upper sides of the 

 leaves. 



