42 Indian Insect Pests. [Vol. I. 



9. THE MAKAI TREE BARK BORER. 



Tomicus sp 



Specimens of a Scolytid beetle, reported by the Officiating Deputy 

 Conservator of Forests, Sibsagar, Assam, to be injurious to the Makai 

 tree, Shorea assamica, have been received through the Director of the 

 Forest School, Dehra Dun. 



The insect proves on examination to be a bark beetle belonging to 

 the genus Tomicus (family Scolytidse). It has not been found possible 

 to determine it with absolute certainty in this Museum, and specimens 

 have therefore been sent to Europe for comparison •} the insect, however, 

 corresponds very closely to the description of Tomicus chalcographus of 

 Linnaeus, an insect recorded as injurious to Abies excelsa and other 

 trees throughout the whole of Europe and also in America. 2 An excellent 

 description of the insect is given in Eichhoff's " Europ'aischen Borken- 

 k'afer" — Berlin, 1881, p. 249 ; his remarks, however, are not given here 

 in full, as the identity of the insect has not yet been fully established. 



In this group of insects the female beetle bores its way into the bark, 

 thus making a tunnel, along the sides of which it deposits its eggs. The 

 grubs on emerging from the eggs, each tunnels on its own account from 

 the place where its egg-shell lay, becomes full-fed, and transforms into a 

 pupa in the barrow, emerging as a beetle which copulates and lays its 

 eggs. The beetle is known to prefer for its attack, trees whose vitality 

 is impaired, and in which therefore the flow of sap is not very strong. 

 Eichhoff has observed, in the case of Tomicus curvidens (and he believes 

 it to be also the case with T. chalcographus), that, when it is unable 

 to find damaged trees, it attacks healthy ones, tunnelling in great 

 numbers into them and thus lowering their vitality and making them 

 suitable for the nourishment of the species. It is true that the flow of 

 sap in the tree may be too strong for the eggs of the actual beetles 

 that first attack it to come to anything, but the tree is so injured that 

 it falls an easy prey to succeeding generations of the pest which emerge 

 from other trees which are in a more advanced stage of the attack. 



Eichhoff has observed in Germany that the beetles emerge in great 

 numbers in April or May ; copulate and lay their eggs, which become 

 fully developed in the end of June or in July, when the second gener- 

 ation of beetles emerges to copulate and lay eggs, becoming fully deve- 

 loped in the autumn and emerging the following April or May. There 

 are thus two complete generations gone through by the insect in Europe, 



1 Specimens of this insect were submitted to Dr. Giinther, who had kindly undertaken 

 to have them examined. He has since reported on them as belonging to a species of 

 Tomicus, which is unnamed in the collections of the British Museum. 



2 For an account of the insect in America, see Packard, U. S. Ent. Commission, Bull. 

 No. 1, 1881, p. 166. 



