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Windermere District.—North. Between Rydal Water and Grasmere (p.),* W. side of Grasmere (d.p.), Elterwater (p.), Skelwith Bridge (p.). S.W. of Clappersgate (p.), near Lady Park (p.), about Bain Gates Inn (p.), Black Crag plantation (p.), near Borwick Lodge (p.). East. Garburn Pass (p.), Troutbeck (p.), Borrans (p.)i N. of Staveley (p.), Long Sleddale (p.). South. Near Ncwby Bridge. ]Vesl. Esthwaite Water, E. side (p.), Sawrey (p.), Claife Heights (p.), Grizedale (p.).
Coniston District.—East. Heald Brow plantation (p.), Coniston Moor plantation (p.). North. Waterhead (p.), High Cross plantation (p.), Hawkshead Hill (p.).
The Longdates.—Chape! Stile (p.), plantations on N. and W. sides of Lingmore Fell, N. of Great Langdale Beck and near Mill Beck (p.), Blea Tarn (p.), N. of Little Langdale Tam (p.), plantations on High Park Fell and Park Fell (p.).
Eskdalc and Wastwater.—Eskdale (p.), near Santon Bridge (p.), near Strands (p.), VV. of Wastwater (p.), Wastdale and Mosedale (p.).
Ennerdale District.—W. end of Ennerdale (p.), about Lamplugh (p.).
Lovienuater.—Larches on S. side (d.p.).
Lorton Vale.—Plantations along and on W. side of the vale (p.), W. of Low Lorton (d.p.), Whinrigg plantation (d.p.).
Buttermere.—Plantation, S.W. (v.b.), N.E. plantation (b.), plantation near Gatesgarth (v.b.).
Borrowdalc District.—Seathwaite (b.), Thornythwaite (v.b.), Rosthwaite (Johnny Wood, &c.) (d.p.), Watendlath (d.p.).
Dcrwent Water District.—Lodore (d.p.), Brandelhow Park and Lingholm (d.p.), Keswick (p.), Great Wood (d.p.), Rakefoot Pike (d.p.).
Hassenthwaite Lake.—N. of lake (p.). West and South West. Mines (?) plantation (b), Combe plantation (v.b.), Hospital plantation (v.b.), Braithwaite (d.p.). South East. Dodd plantation (v.b.), Millbeck (b), Latrig (d.p.).
Thirlmere District.—North. Shoulthwaite plantation (v.b.), St. John's Vale (p.). East and West. Plantations (b.), chiefly (v.b.).
Ullswater District. — West. Matterdale (p.) and (d.p.), W. side of lake (p.), Glenridding (p.). South. Hartsop (p.).
Hawes Water.—Larches at S. end (p.).
The distribution of the saw-fly and the intensity of the attack will be readily understood from the accompanying map.
Means of Detection.—If the larvae are present in any number there will be sufficient evidence of their presence in the number of defoliated twigs, which give a brownish winter appearance to the branches when seen from a distance. If the larvae are still young their presence can be detected by the brown and slightly curled appearance of the green leaves near the ends of the twigs, which is due to the young larvae partially devouring them, usually along one side. In the case of larvae occurring at the top of tall trees, if their presence cannot be detected by the defoliation of the twigs of the lower branches, it is generally indicated by the small green cylindrical faecal pellets which may be found round the base of the tree; these are figured in
* NOTH.—(p.) indicates that the insect was present, though in such small numbers that its presence would not be noticed by an untrained observer, (d.p.) in these plantations or groups of trees the insect was distinctly present, (b.) indicates that the tree, were badly attacked, and (v.b.) indicates that the attack was very bad, the trees being completely defoliated.
MacDougall's paper. A further means of detection has already been mentioned, namely, the dying off and curling round of the short terminal shoots, which is caused by the injury inflicted by the females in depositing their eggs.
THE LAKE DISTRICT
Showing hhe distribution of The Large Larch SawFly (Nemahus eriehsoni.)
n 11 ij
Natural Enemies.—The most important factors m the natural control of the saw-fly which have so far been discovered are birds, and, as will appear strange, the small Field Vole— Microtus (Arvicola) agrestis.
When the larvae were in the: earlier stages it was found that the three species of Tits—the Great Tit, Cole Tit, and Blue Tit—: fed upon them to a" considerable extent. They were also assisted by Chaffinches, which were found feeding on the fullgrown larvae. In addition to these birds, which perform no little service, great destruction of the larvae was effected by the Rooks, Jackdaws, and Starlings which were to be seen in large flocks in and about the more seriously attacked plantations. They not only fed upon the larvae on the trees but also followed them on to the ground when about to spin their cocoons beneath the turf. When the larvae had reached this stage one frequently found that the Rooks had riddled the turf round the bases of the trees with holes in search of the larvae.
Birds do not normally care for such resinous larva? as those of N. crichsoni, but the present case is an example of a phenomenon which sometimes occurs when an insect assumes unnatural proportions and becomes a pest, and where the presence of a large amount of food temporarily alters the feeding habits of many of the birds of that locality.
During the winter months when the larvae are enclosed in their tough cocoons they are safe from the attacks of their avian enemies, but it was discovered as a result of observation and experiment that the small Field Vole, Microtus agrestis, Flemming (Fig. i), proves itself of very great service in extracting the larvee from the cocoons and eating them. This small rodent burrows beneath the turf and litter round the bases of the trees in search of the cocoons; having found a cocoon it nips a small piece off one end and draws out the enclosed larva,* which it then devours. The presence and activity of the voles is attested by the numbers of empty cocoons gathered in small groups in the runs that they have made and the teeth-marks of the voles can be readily distinguished on the empty cocoons (see Fig. 2). . During last winter (1907-8) these animals destroyed large numbers of the larvae in all the plantations on the Thirlmere watershed which were badly attacked. From observations made in different plantations I calculated that they had destroyed about 25 per cent, of the pupating larvae. Further, dissections of their stomachs and microscopic examina
• "the saw-fly larva remains in the larval stage in the cocoon until about May of the following year, when it changes into the pupa.