INDIRECT INJURIES CAUSED BY INSECTS. 



165 



found in young pears, on opening them, a larva of this genus. ^ 

 A little moth likewise is mentioned by Mr. Forsyth as very 

 injurious to this tree.^ 



But of all our fruits none is so useful and important as the 

 apple, and none suffers more from insects, which according 

 to Mr. Knight are a more frequent cause of the crops failing 

 than frost. Here, as in the pear-trees, the bark, and con- 

 sequently the whole tree, suffers from the larvae of Carpocapsa 

 Woeberana, and of Tinea corticella L., as well as of a Scolytus 

 nearly related to S. destructor, but perhaps distinct, which I 

 found infesting it in Guernsey in 1836 ; and in Austria the 

 larva of another beetle ( Trypodendron dispar) pierces into the 

 heart of young healthy trees, and destroyed (ikf. Schmidberger) 

 several of his stock. The sap is often injuriously drawn off 

 hj Psylla mali'^'^ and by a minute Coccus, of which the female 

 has the exact shape of a muscle shell (C arborum linearis 

 Greoffr.), and which Reaumur has accurately described and 

 figured.^ This species so abounded in 1816 on an apple-tree in 

 my garden, that the whole bark was covered with it in every 

 part ; and I have since been informed by Joshua Haworth, 

 jun. Esq., of Hull, that it equally infests other trees in the 

 neighbourhood. Even the fruit of a golden pippin which he 

 sent me were thickly beset with it. But the insect which 

 most injures our apple trees by drawing off their sap, and which 

 has been known in this country only since the year 1787, is 

 the apple-aphis, called by some the Coccus, and by others the 

 American blight. This is a minute insect, covered with a long 

 cotton-like wool transpiring from the pores of its body, which 

 takes its station in the chinks and rugosities of the bark, 

 where it increases abundantly, and, by constantly extracting 

 the sap, causes ultimately the destruction of the tree. Whence 

 this pest was first introduced is not certainly known. Sir 

 Joseph Banks traced its origin to a nursery in Sloane Street; 

 and at first he was led to conclude that it had been imported 

 with some apple-trees from France. On writing, however, 

 to gardeners in that country, he found it to be wholly unknown 



1 Reaum. ubi supr. 475. 2 On Fruit Trees, 271. 



3 Kbllar, on Ins. inj. to Gardeners, &c. 256. ^ Ibid. 278. 

 5 Reaum. iv. 69. t. 5. f. 6, 7. 



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