ON IHE LIFE HISTORIES OF FOREST INSECTS 27 



by the beetles. The species in question, which in most cases will var\' with 

 the species of tree you are examining, will only attack fresh green sappy 

 bast, and by some unerring instinct it is always able to discover for its 

 egg-laying operations newly felled trees, if haply there be such in the 

 area ; or if in a forest untouched and untended by man, new windfalls or 

 sickly, unhealthy, or dying trees. If such are perchance unavailable, 

 it must go to the green healthy standing trees to oviposit, since dead 

 trees with no fresh sappy liber in them are useless for its purpose, as 

 they would afford no sustenance to the young grubs when the\' hatch 

 from the egg. 



Many of the Buprestidae and Cerambycidae are also possessed of this 

 wonderful instinct for detecting newly felled trees. Whilst on t(nir in 

 Goalpara in May igo6 several green perfectly healthy sal-trees were felled 

 in the forest one morning. On visiting the trees the following morning in 

 company with the Divisional Forest Officer, 

 Mr. W. F. Perree, we found a hundred or two 

 of the large longicorn beetle Hoplocerauibyx 

 spinicornis crawling about in the shade of the 

 outside bark nearest the ground at points 

 where the bark did not actually rest on the 

 soil. Until we parted the undergrowth sur- 

 rounding the fallen trunk the insects were in 

 complete darkness, and they were all per- 

 ceived to be intent on pairing or egg-laying. 

 This proved the first recorded instance of the 

 operation of egg-laying by longicorn beetles 

 in the Indian forest having been observed. 

 Further careful examination showed that the 

 forest contained hundreds and thousands of 

 these beetles ; and yet there was no sign of 

 them w^hatever until sought for in their day 

 shelters, as the insect is not a diurnal one. 

 I would not be understood to say that there 

 are no diurnal longicorns. There are. The 



brightly coloured Thysia waUichii is a case in point, and we saw some 

 specimens of it sitting in the sunlight on adjacent standing sal-trees on the 

 morning in question. This instance is quoted to show that it is (]uite 

 possible for the forester to find some of his pests in the forest during 

 the day, if he knows where to search for them, and so to make himself 

 acquainted with their abundance at the seasons at which they are on the 

 wing and egg-laying. He is thus in a position to know what to expect 

 in the w^ay of insect attacks during the next few months. In the case of 

 the Hoplocerauibyx in question, the insect was proved to be in enormous 

 numbers, and its life history being understood, the early barking of all 

 felled trees became imperative, since it was known that once the grub 



Fio. 17. — Thysia wallichii, 

 a diurnal longicorn. Assam. 



