Zoologi^\ 1 53 



is very rapid, and their numbers compensate for their diminutive size, 

 80,000 being sometimes found in a single tree. 



By carefully examining the bark it may be readily ascertained which trees 

 are infected. The bark will appear perforated with small holes in various 

 parts, and little patches, similar to fine sawdust, will be found upon its 

 rough surface, and at the foot of the tree. This examination should take 

 place whilst the insect is in the larva state, and, if the evil has proceeded 

 far, the tree should be immediately cut down, and every portion of the 

 bark taken off. Even this operation is not sufficient to destroy the enemy : 

 the bark must be burned. But where the tree is only slightly infected, it 

 may be done over with the oil of tar. This, as I have found, will pene- 

 trate the bark, and destroy all the larvae lying towards the surface. April 

 is perhaps the best time of the year for this operation, as the perfect insects 

 are then working their way towards the surface, and will be obliged to eat 

 through the bark freshly imbrued with the liquid. Those healthy trees in 

 the vicinity of the infected, which it is a particular object to preserve, ought 

 likewise to be subjected to the same process, as an effectual preservative 

 against the approaches of the insect. It has been suggested that some 

 mineral poison, as corrosive sublimate, might be advantageously mixed 

 with the oil of tar ; but I am not prepared to say whether the tree itself 

 would not be injured by such an ingredient : the experiment has been 

 tried, and the test of experience will alone determine. 



Those who may wish for further information respecting the form and 

 characters of this insect will find an elaborate description of it, together 

 with an admirable figure, given by Mr. Curtis in his Illustrations of British 

 Entomology^ No. 11. fig. 43. There is also an able paper upon its habits, 

 and a detailed account of the destruction it has occasioned among the elms 

 in St. James's Park, published by Mr. M'Leay in the Edinburgh Philosophi- 

 cal Journal^ 1824, p. 126. Specimens of the insect, and portions of the 

 bark exhibiting its very curious progress, I shall be happy to show, in illus- 

 tration of these remarks, which are with deference offered, with a view to 

 excite the attention of those interested, and to provoke further enquiry 

 into this highly important subject; and I am more especially inclined to do 

 so, as the pest appears to be widely spreading in this neighbourhood, and, 

 if not timely checked, we may soon expect to see its destructive effects 

 visible in some of the ornamental trees in the justly admired walks of the 

 university ; nor will this fear be considered imaginary when it is stated 

 that a similar insect, a few years since, caused such devastation in the Hartz 

 Forest in Germany as threatened to suspend the mining operations of 

 that extensive district. — /. Deck. Cambridge^ Nov. 6. 1827. (Cambridge 

 Chronicle, Nov. 9. 1827.) 



[B.] 



To Mr. DecJcy on the Decay of the Elms in Catherine Hall Grove. 



Sir, In reply to your letter in the Chronicle of the 9th of November, I 

 am happy to be able to agree with you that gault or blue clay will not 

 destroy elms, as I know healthy elms which grow wholly in blue clay. 

 I must, however, differ from you totally in imputing the death and disease 

 of the trees mentioned to the ravages of the Scolytus destructor. The 

 grounds of my dissent are the following : — 



1. My cottage stands within a few poles both of a fine elm grove and a 

 wheelwright's timber-yard, and although thousands of the Scolytus de- 

 structor are annually hatched in this timber-yard, no healthy tree in the 

 contiguous grove has ever been injured by them. 



2. The wheelwright himself, familiar enough with the larvae of the Sco- 

 lytus, although not by these names, attests that, in stripping the bark off 



