SA W-FLIES AND WOOD- WASPS. 



575 



Saw-Flies 

 injurious to 

 fruit trees. 



Tenthredinidce, but is most frequently nine, especially in the more typical 



sub-families, in which the joints are long, cylindrical, and 



well-marked. In one sub-family, however, the short, thick Antenna of Saw 



antennae are composed of only three well-separated joints ; Flies. 



the scape, a short joint, and a long terminal one composed of 



several fused together. Sometimes this third joint is bifid, each antenna 



being thus double nearly to the base. 



Our fruit-trees often suffer severely from the attacks of the larvae of various 

 saw-flies. Those best known to ordinary observers are probably the small 

 greenish or yellowish black-dotted larvae which frequently 

 strip our gooseberry and currant bushes of all their leaves, 

 and which develop into small black and yellow four-winged 

 flies about half-an-inch in expanse, belonging to various species 

 of the great genus Nematu (Panzer. ). But these bushes are li- 

 able to the attacks of the larvae of saw-flies belonging to other sub-families than 

 the Nematince, and also by the larvae of various Lepidoptera and other insects. 

 The Siricidce, or wood-wasps, burrow in the larva state in timber, with which 

 they are frequently imported into this country. The commonest and most 



conspicuous species is 

 Sirex gigas (Linn.), a very Wood-Wasps 

 formidable - looking in- (Siricidce). 

 sect, the large females of 

 which sometimes measure nearly two 

 inches across the wings, though many 

 specimens are much smaller ; for wood- 

 feeding insects, as a rule, vary very 

 much, both in size, and in the length of 

 time which they require to reach matu- 

 rity. It is black and yellow, and the 



Fig. 53.-Sirex gigas. Male. Nat. size. emale j has a stout ovipositor projecting 



behind the body for about one-third of 



its length. The abdomen of the male, on the other hand, terminates in a 

 rectangle. These insects 

 will sometimes emerge from 

 planks of deal or pine, 

 which have been built into 

 the floors or fittings of a 

 house, and make a loud 

 buzzing, which has some- 

 times led to their beingmis- 

 taken for hornets, but they 

 are really quite harmless. 



The (jrollicolce,, or gall- 

 flies, are far better known 

 by the galls which grow 

 upon the leaf or stalk in 

 which they have deposited 

 their eggs than by the flies 

 themselves, which are gen- 

 erally small shining black 

 or reddish insects, with 

 long antennae and trans- 

 parent wings, with the very Fig. 54. Sires gigas. Female. Nat. sh 



