DESTRUCTIVE INSECTS. 293 



be called, is always of a deep, lurid red, showing their 

 affinity to the cochineal insect, indigenous to the 

 Opuntia cochinilifera in South America. 



It has been stated that this coccus is the sole 

 cause of the disease called canker; but this is a 

 mistake, because cankered trees, both those of the 

 orchard and forest, are every where seen unaccom- 

 panied by this or any similar insect. It is very true, 

 however, that the dismemberment an/?, distortions of 

 the bark caused by either constitutional or accidental 

 canker, are very likely to attract insects to nestle in, 

 and this coccus as well as others ; but the effects of 

 constitutional canker may always be distinguished 

 from those occasioned by the insect in question. It 

 has also been said that the American blight was 

 introduced about 1788 from France by the late Cap- 

 tain S. Swinton, R. N., who had a foreign nursery at 

 that time, behind No. 6, Sloane Street, Chelsea. But 

 however, true this may be, there is no doubt the same 

 insect was in England long before that period ; as old 

 crab trees standing in woods and hedges in the middle 

 counties were then, as now, covered with it. An 

 insect of the same family is frequently seen on the 

 underground stems of lettuce, endive, and dandelion. 



Of all these insects, the mealy one infesting pines, 

 and the last described so pernicious in orchards, are 

 the most destructive ; they both prey on the vitals 

 of the plant, and their introduction among such as are 

 clean should be carefully guarded against. The first 

 are killed or banished by a wash composed of the 



