i9io.] 



Official Circulars and Notices. 



has led the Board to place the Sawfly among- the dangerous insects 

 scheduled under the Destructive Insects and Pests Order, the presence 

 of which on any plantation must at once be reported to the Board. 

 They are also engaged on an investigation of the extent to which it 

 prevails in this country in the hope of discovering some preventive 

 or remedial measures. Every occupier of any premises on which the 

 insect is found, is bound therefore to report the discovery under a 

 penalty of ten pounds, but few cases have been reported chiefly on 

 account of the inability of most persons engaged in forestry to identify 

 the pest, or recognise the symptoms of an attack. The Sawfly remains 

 in its larval state for only a few weeks of the year, and for some part 

 of that time it is very small and, consequently, easily overlooked. 

 The appearance of an attacked tree, however, is such that for a much 

 longer period the characteristics can be distinguished by an expert. 

 In spite, however, of this extension of time it is not possible for the 

 Board's Inspectors to examine every larch plantation in Great Britain, 

 and the Board feel it incumbent on them to ask for the assistance of 

 every person interested in forestry in tracing the presence of the 

 infestation. 



The search may be conducted in two ways : — 



1. The actual insect may be looked for as (i) egg embedded in the 

 shoots of the tree, (2) caterpillar feeding on the green needles, (3) 

 cocoons lying in the ground or among the long grass, (4) adult on 

 the wing. 



2. The larch trees may be examined for signs of Sawfly attack, even 

 though no insect can be found. 



The caterpillars or larvae of the Large Larch Sawfly may be first 

 looked for towards the middle and end of June. In 1909 the first seen 

 were not discovered till July 4th, but they were evidently some days 

 old and the season was rather late. They appear in considerable 

 numbers on the lower branches of the larch, generally towards the 

 terminal shoots in which the eggs are laid. As they grow older they 

 advance towards the stem, and eventually may be found wherever there 

 are any needles. Larvae begin to spin up their cocoons in July. In 

 1909 the last caterpillar was seen on August 31st, but in other years 

 they might be found later. 



When very small they are not easily noticed, but they grow rapidly, 

 and when full grown are about three-quarters of an inch long, with 

 round black heads, three pairs of black thoracic legs, and seven pairs 

 of abdominal legs of a greyish green, the same colour as the rest of 

 the body. 



The caterpillars feed at first in clusters, but afterwards they separate 

 in search of food. They assume various characteristic positions, a 

 common one being with their "tail end" curled round the shoot xyn 

 which they are feeding. When disturbed they erect the hind segments 

 of the body over the front ones. The larvae of the Large Larch 

 Sawfly can be distinguished from other larvae that may be found on 

 the larch by the following characters : — 



Moth caterpillars. Nematus erichsoni. 



Legs never more than sixteen. The caterpillars have twenty 

 If they are geometer cater- legs, 

 pillars they progress by a looping 



