30 INDIAN FOREST INSECTS 



Fortunately, however, some of the most serious of forest pests, the 

 large class of bark- and wood-boring insects (and their predators and para- 

 sitic foes, the friends of the forester), can be studied by every Forest Officer 

 out in the forest in a comparatively simple manner. 



All that is required is that two or three green healthy trees of the 

 species whose pests it is wished to study should be felled in some con- 

 venient locality. The trees should not be felled in deep shade, nor in 

 positions in which they will receive the full force of the midday sun, which 

 will dry them up too quickly. 



By visiting such trees, say, weekly or fortnightly, and stripping off a 

 piece of bark so as to examine the bast layer on its inner side and the outer 

 sapwood on the stem itself, a vast amount of information of importance 

 to the Forest Officer can be ascertained. 



The common bast-eating beetles who infest this particular tree will 

 quickly make their appearance — buprestid, cerambycid, and scolytid, perhaps 

 also elaterid and curculionid. The insects appearing will of course be 

 the mature forms only, and they will at once commence egg-laying on 

 the outer bark, or in crevices in the bark, or tunnel into the tree and eat 

 out the pairing-chambers and egg-galleries in the bast and sapwood. 

 The dates of such operations should be noted. If the inner side of the 

 bark (the bast) is examined, small elongated galleries may be observable 

 with a series of little notches set therein at regular intervals all the way 

 up on either side (cf. fig. 22). These are made by bark beetles, Scolytidae, 

 and in each notch is an egg. Careful observation may also show the 

 presence of several of the insect friends of the forester. The clerid 

 Thanasimus (p. 186), for instance, may be present on the outside of the 

 bark, or the Niponius (p. 103) in one or more of the egg-galleries of the 

 bark beetles, or numerous tiny airy flies hovering about, Ichneumons 

 (p. 474), Chalcids (p. 507), or Bracons (p. 480), all parasitic upon the insect 

 pests, and all there with intent to lay their eggs in the galleries of the 

 bark-boring insects. 



Little individual galleries half an inch or less may be visible already 

 in the sapwood, made by buprestid or cerambycid grubs. 



The visit made a fortnight later will show many more galleries present 

 in the inner surface of the bark : and those first observed will now have 

 numerous off-shoot galleries on either side made by the grubs which have 

 hatched out from the eggs laid by the bark beetles. At the head of each a 

 grub will be seen. The buprestid and longicorn grubs will also be larger 

 and their galleries longer and broader. Amongst the numerous galleries 

 pink larvae may be seen. These are predaceous Thanasimus or Niponius 

 larvae feeding upon the b irk-beetle ones. Or tiny white maggots may 

 be visible attached to some of the bark-boring grubs (cf. fig. 360) or to the 

 buprestid or cerambyx grubs. These are parasitic grubs hatched from the 

 eggs of the Ichneumon, Bracon, and other flies we saw hovering about on 

 our first visit. 



