170 HYMENOPTEKA (WOOD WASPS). 



pupating in the cocoon in the very early spring. Some live 

 in wild grasses at the headlands, hedges, and woods, so that wo 

 have constant fresh infestations coming. 



Prevention. — The only way we can check this pest is to keep 

 it down in our fields. If the stubble is simply ploughed in after 

 an attack of corn sawfly, unless very deeply, a large number of 

 the insects will hatch out and escape from the ground. It is 

 advisable where this pest has been very bad to scarify the fields 

 and harrow the stubble together and burn it on the fields : by so 

 doing all the larvse in the "gratten" are destroyed, and thus 

 much subsequent harm prevented. Of remedies naturally there 

 are none. 



Two other Sawflies are often injurious, namely, the Apple- 

 Sawfly {Hoplocampa iestvMnea), which eats the young apples, 

 and the Pine Sawfly (Lophyrus pini), which is sometimes most 

 injurious in pine-forests. 



Wood "Wasps (Siric/iJce). 



The second group of Phytophagous Hymenoptera are the 

 Wood Wasps or Siricidce. The Sirex-flies have a long freely 

 projecting ovipositor, by means of which the female places her 

 ova in the wood of trees, especially pines. Two species are 

 destructive to pine-trees in England, namely, the Giant Sirex 

 {Sirex gigas) and the Steel Blue (S. juvencus). Both are large 

 insects, the former species often being an inch and a quarter 

 long in the female, with four tawny wings and black and yellow 

 body ; S. juvencibs is somewhat smaller, and beautiful steel-blue 

 in colour. The ova laid under the bark of the pine-trees hatch 

 into white, nearly footless, larvse, which eat their way into the 

 very heart of the wood, forming long tunnels which are partly 

 blocked up as they progress with their "frass." They seem to 

 live in this position some nine months, and pupate somewhere 

 near the bark, so that in the summer when the Sirex is mature 



