108 BRITISH INSECTS 



leaves resemble the caterpillars of moths, but have 

 more than five pairs of prolegs sometimes as many 

 as eight pairs ; but those which burrow in stems or 

 wood are white, fleshy grubs, with hard heads. There 

 are three families in the sub-order. 



The stem saw-flies, so called because their larvae 

 feed in the stems of plants, make up the little family 

 Ccpkida. They are the least specialized of all the 

 Hymenoptera. The pronotum is elongate, and instead 

 of being intimately connected with the mesonotum, is 

 free and mobile a character which is not found in 

 any of the succeeding families. The corn saw-fly 1 is 

 not uncommon in the South of England. The female 

 inserts an egg a little below the first joint of a young 

 corn-plant, and the grub eats its way upwards, often 

 boring through all the joints. When full-fed, it re- 

 traces its course, and spins its cocoon close to the 

 roots, first, however, felling the plant by partially cut- 

 ting through the straw at the base. 



The family Sivicidce is represented by two British 

 species viz., the giant wood-wasp, 2 and the steel- 

 blue wood-wasp. 3 The former is not unlike a hornet 

 in its coloration, but is quite harmless. The long, 

 horn-like process at the extremity of the female's 

 abdomen is not a sting, but an ovipositor, by means of 

 which she bores holes in the solid wood of trees and 

 inserts her eggs. The white grubs feed on the wood, 

 in which they make long tunnels. It is said that they 

 may become full-fed in seven or eight weeks ; but 

 usually the life-history appears to be much more pro- 

 tracted, and instances are recorded of adult wood- 

 wasps issuing from timber long after its incorporation 

 in a building. Coniferous trees are usually attacked, 

 1 Cephas pygm&us. 2 Sirex gigas. 3 S.juvencus. 



