50 THE TAIGA, OR CONIFEROUS 
arborea) of Europe just reaches the south of the taiga, 
but the tree-frogs of North America have a more 
northerly extension. 
In insects the northern forests are rich, for the 
perennial vegetation feeds many herbivirous forms, 
and many carnivorous or parasitic forms prey upon 
these. Many of the beetles especially are important 
pests from the point of view of the forester. 
As examples of wood-eating forms we may mention 
the wood-wasps (Sirex), of which a large species (S. 
gigas) often appears in summer-houses or other wooden 
erections in Britain, where it has been introduced with 
pinewood. The adult female has a boring apparatus, 
by means of which she bores a hole in trunks of pine 
trees in order to lay her egg at the bottom of the 
excavation. The wood-wasps are preyed upon by 
ichneumon flies, whose delicate senses enable them to 
find the burrows of the wasps, when they insert their 
long ovipositors and lay their eggs close to the wasp’s 
egg, so that the resultant larvae may prey upon the 
wasp larva. There is here a singularly delicate adjust- 
ment between host and parasite, comparable to the 
relation which exists between the length of the pro- 
boscis of certain butterflies and the length of the tubes 
of the flowers which they visit. 
Another form which feeds in the pine woods is the 
pine saw-fly (Lophyrus pini), whose larvae feed upon 
the needles, sometimes in countless numbers. 
Wild bees also occur in the woods, the forms which 
store up honey extending much further north in the 
Old World than in the New. In Asia wild honey bees 
reach the Arctic circle, while in North America, accord- 
ing to Marshall, they scarcely pass latitude 50° N. The 
honey is greatly prized by bears, who rob the nests 
