'204- INDIRECT INJURIES CAUSED BY INSECTS. 



seem quite covered with little locks of white cotton; which 

 appearance is caused by a filamentous secretion transpiring 

 through the skin of the animal, in which they envelop their 

 ecrgs. Where they prevail they do great injury to the 

 plant by subtracting the sap from its foliage and fruit, 

 and causing it to bleed. — And to close the list, you are 

 perfectly aware of the eagerness with which wasps, flies, 

 and other insects, attack the grapes when ripe, often leav- 

 ing nothing but the mere skin for their lordly proprietor. 

 There are some of these creatures that attack indiscri- 

 minately all fruit-trees. One of these is the Tettigonia 

 septendecim, F., (so called because, according to Kalm, it 

 appears only once in seventeen years a .) The female ovi- 

 posits in the pith of the twigs of trees, where the grubs 

 are hatched, and do infinite damage both to fruit- and 

 forest-trees 5 , — Another, the caterpillar of the butterfly 

 of the hawthorn, (Pajoiiio Cratagi, L.) which in 1791, in 

 some parts of German}^, stripped the fruit-trees in general 

 of their foliage c . — In France also in 1731 and 1732 that 

 of a moth which seems related to the brown-tail moth 

 (Bombyx phceorhxa^ F.), whose history has been given by 

 the late Mr. Curtis, was so numerous as to occasion a 

 general alarm. The oaks, elms, and white-thorn hedges 

 looked as if some burning wind had passed over them and 

 dried up their leaves; for, the insect devouring only one 

 surface of them, that which is left becomes brown and dry. 

 They also laid waste the fruit-trees, and even devoured 

 the fruit; so that the parliament published an edict to com- 

 pel people to collect and destroy them : but this would in 

 a great measure have been ineffectual, had not some cold 



a Travels, ii. 6*. b Collinson in Philos, Tram. liv. x. 05* 



c Roscl, I. ii. 15, 



