TREES AND SHRUBS 



lj in. to 1.1 in., and the ovipositor being about half as long as the 

 body. By means of the "saw" contained in the ovipositor the insect bores 

 into the bark of Spruce and Silver Firs, and occasionally Larch, depositing 

 1 egg in each hole made. The length of the larval stage is not easily 

 ascertainable, but the perfect insects emerge from July to September. 



The Steel-blue Sirex (Sirecc juvencus) is slightly smaller than the first 

 species, and is usually of a dark steel-blue colour, with red-brown feet ; in 

 the males several segments of the abdomen are rusty-red. The wings in 

 both sexes are yellowish. This species prefers the Scots Pine. 



It is impossible to destroy the larvae in infested trees. All that can 

 be done is to cut down such trees, and remove all sickly trees and fallen 

 brandies and trunks. The timber is of little value, save as firewood. 



The next section of the Hymenoptera contains a large number of boring 

 insects known as Saw-flies, the boring instrument being modified into a 

 pair of toothed saws, which are used for cutting incisions in leaves, or in 

 the tender bark of twigs, in which to deposit the eggs. The larva? much 

 resemble caterpillars in appearance and habits, and the pupa? are enclosed 

 in cocoons. 



The Pine Saw-fly {Lophyrus pini) bores into the needles of Scots Pine, 

 and deposits a large number of eggs. The female is pale yellowish-white, 

 with black head and breast, the wings expanding £ in. The male is 

 black, and the wings measure h in. across. The light greenish-yellow larvae 

 are gregarious, and do much damage by gnawing and totally destroying the 

 needles. There may be two generations in the year. In gardens and young 

 plantations hand-picking may be found an effectual remedy, but in older 

 woods it is impossible to cope with the pest. 



There are several species of Lophyrus which attack Conifers, and also 

 some species of Lyda. The latter are semi-social, spinning a common web, 

 but each also spinning an inner tube for itself. Various species attack fruit- 

 trees, Alders, Birches, and Willows. 



The Gooseberry and Currant Saw-fly (Nematus ribesii) is very trouble- 

 some in plantations and gardens in some seasons, and is probably the most 



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