i88 
Yorkshire Naturalists at Dent. 
the stream being in many parts solid rock, worn deeply into gulleys and 
pot-holes, and holding few loose stones which could afford a foothold 
for the inhabitants. Here and there deeper and more tranquil portions 
occurred with more suitable bed. Below Dent Bridge the river bed was 
of a different type, consisting in great part of areas of shingle and 
sediment, with more vegetation. The most prominent inhabitants were 
as usual, larvae of Stone-flies, May-flies and Caddis-flies, associated 
with Ancylus (Freshwater Limpet), especially plentiful near Cowside, 
and Gammarus (Freshwater Shrimp). The Stone-fly larvae, besides the 
more usual types, included both Perla cephalotes and P. carlukiana. 
The May-fly larvae included Heptagenia, Siphlonurus, Ecdyonurus , and 
Baetis. The most numerous Caddis larvae were Hydropsyche , Plectroc- 
nemia, and Rhyacophila. The minute bean-shaped cases of Hydroptila 
were plentiful. On the upper surfaces of the submerged flat stones, 
the long, sediment entangling galleries containing Tinodes wacheri 
were conspicuous and plentiful, as were the tubes inhabited by the 
small Ghironomid larvae. Simulium larvae and pupae occurred. 
Planarians were not noticed and the Caddis, Agapetus, usually so common 
in upland streams, were not numerous here, though plentiful in other 
streams. Below the bridge the minute Hemipteron, Micronecta 
minutissima , associated with the beetles, Bry chius elevatus and Deronectes 
borealis occurred in numbers. 
Perhaps the most striking feature of the stream was the enormous 
number of egg-masses of Caddis and May-flies, and it was most interesting 
to watch the delicate-winged May-flies descending below the water and 
affixing their eggs to the undersides of the stones. 
Helmside Beck was of interest. The lower portion running through 
the gorge was a rapid torrent with stoney bed and having a fauna similar 
to that of the Dee, including the larger Stone-fly larvae. In the upland 
region, the stream flowed across the open moor, with much slower current 
and considerably more sediment in its bed. Here occurred larvae of the 
May-fly, Potamanthus luteus, which was not noted elsewhere. In the more 
tranquil pools in this part of the stream Callicorixa praeusta occurred, 
and on the surface Velia currens and Gerris. Gammarus was very plenti- 
ful. Flying about the stream were many Dragonflies [Pyrrhosoma 
nymphula), which probably came from a neighbouring pool. In the 
bed of the stream the thread-like ‘ worm,’ Gordius, was particularly 
numerous. The early stages of this organism are passed parasitically 
in the larvae of the Alder-fly and other aquatic types. Thence trans- 
ferred into the bodies of carnivorous beetles they pass a second period 
of parasitism, finally becoming free and mature in the water, depositing 
eggs which hatch into a larval form, which enters the first host and 
commences its strange life history. Alder-flies, Sialis fuliginosa, were 
flying in considerable number about here. 
In many of the upland streams, especially those about Coomb Scar, 
enormous growths of the Diatom, Gomphonema geminatum, occurred, 
whose branching tubes formed dense sponge-like tufts on the wet surfaces 
of the partially-submerged stones, and formed a conspicuous feature 
in the stream. 
Ecology of Dentdale (A. Malins Smith) : — The ecological charac- 
teristics of the upper part of the dale between Dent and Cowghyll, seem to 
depend on the fact that the Yoredales have mainly contributed to its 
soils. Containing, as they do, shales and sandstones, as well as lime- 
stones, they form a soil so slightly acid that certain plants characteristic 
of limestone can flourish, yet not basic enough to support a typical 
limestone flora. This was seen in the meadows bordering the river. 
Two indicator plants may be taken as a test. Poterium Sanguisorba , 
the Salad Burnet, so abundant on limestone grassland, was practically 
absent, while on the other hand Rumex acetosa, the Sorrel Dock, which 
The Naturalist 
