136 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



18. Forest Insects on the Culbin Sands. 



By J. W. MUNRO, D.Sc. 



The Forestry Commission's operations in afforesting the 

 barren Culbin Sands are of special interest to all engaged in 

 agriculture and forestry. They involve the solution of a 

 multitude of problems created by the nature of the area to be 

 planted, problems not wholly silvicultural, which when solved 

 will contribute considerably to our knowledge of the practice of 

 forestry. 



The Culbin Sands form an isolated stretch of land cut off as 

 it were by its own peculiar formation. They have, however^ 

 within comparatively recent years been linked up in the west 

 with the terra firma of the neighbouring lands by the planting 

 of what is known as the Low Wood, part of which has been 

 recently felled, and part, unfortunately, burned. At the eastern 

 end of the sands planting has also been carried out, but does 

 not form here such an extensive link as does the Low Wood, 



The planting of the Low Wood, and especially the felling and 

 burning of part of it, has a definite bearing on the Commissioners' 

 extended afforestation work, in that they have introduced the 

 question of protection against insect pests into the already 

 complicated problems of fixing and planting moving sands. 

 The Low Wood, both in the felled and in the standing areas, 

 is now the home of a considerable number of pine-dwelling 

 insect pests. 



A study of the forest insect conditions prevailing on the 

 Culbins is of considerable interest, and suggests the way in 

 which the insect conditions prevailing in our Scottish wood- 

 lands may have arisen. The most important forest insects 

 occurring in the Lov/ Wood are Hylobhis abietis, Myelophilus 

 piniperda, Pityogenes bidentatus and P. quadridens, Hylastes ater, 

 Tomicus acuminatus, and Pissodes pint. In addition to these a 

 number of less injurious beetles occur, e.g. Rhagiiim i7idagator, 

 Pityophthorus piibescens, and Ernobius nigrifius. With these are 

 present the usual useful pine insects — the "Ant-beetle" (Clerus 

 formicarius), two species of Rhizophagus, the Scottish Ips 4 

 pustulafa, various Staphylinid beetles, and, most interesting 

 of all, a Braconid parasite on the grub of Hylobhis. 



All these insects are represented in the surrounding region, 



