DAMAGE TO ELM TREES. 189 



by the wood and bark on which it has fed, and for this purpose 

 the bold wrinklings of the upper surface afford as useful means 

 of progression to the insect as the ventral scales of the snake 

 do to the reptile. The head is hard and scaly, and the jaws 

 are exceedingly powerful. One of these larvae is shown on 

 Woodcut XX. Fig. c. 



When nearly full-fed, the greater number of the larvee 

 burrow directly into the tree, making holes about half an inch 

 iu depth, at the bottom of which they are qiute safe, even 

 thougli tlie bark should fall off, as is often the case. Tliey are, 

 further, protected from weather and the eyes of hungry birds 

 by the ' frass,' or digested remains of the wood, which fills up 

 the tunnel behind the larva. It is much doubted whether the 

 Scolytus ever attacks a healthy ti'ee, principally, as is con- 

 jectured, because in such trees the burrows of the insects are 

 tilled with sap, which not only drives out the Beetles, but pre- 

 vents their eggs from being hatched. Still, when a tree 

 becomes unhealthy, the attacks of the Scolytus prevent it from 

 recovering itself ; and such serious damage has been done by 

 this insect to our trees, especially the elms in and about 

 London, that the attention of entomologists has long been 

 directed to the subject, in hopes of discovering some device by 

 which the ravages of the Scolytus may be checked, if not 

 altogether stopped. As yet, however, no scheme has suc- 

 ceeded. Various plans have been suggested, such as injecting 

 poisonous fluids into the hole made by the mother Scolytus. 

 This might possibly answer, provided the operator could be 

 sure of discovering all the holes, and provided that the liquid 

 did not kill the tree as well as the insect. The ' Grishurst 

 Compound ' would do as much in this way as anything could, 

 but it cannot be employed on a large scale. 



At present, the opinion seems to be that the only plan which 

 offers the least probability of success is a ' stamping out ' pro- 

 cess, similar to that which saved us in the time of the cattle- 

 plague. By this plan, all trees which are visibly attacked by 

 the Scolytus are to be cut down, and stripped of their bark and 

 the outer layer of wood, which are then to be burned, so as to 

 destroy the Scolytus, its larvae, pupae, and eggs. 



Dr. Chapman states that all the species of Scolytus are in the 

 habit of fighting with each other. Tney ' have a fashion of 



