206 INDIRECT INJURIES CAUSED BY INSECTS. 



their eggs. 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 

 leaving nothing but the mere skin for their lordly pro- 

 prietor. 



There are some of these creatures that attack indis- 

 criminately all fruit-trees. One of these is the Cicada 

 septendecim, (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 b . Another, the caterpillar of the butterfly 

 of the hawthorn, (Pier is Crat&gi) which in 1791, in some 

 parts of Germany, stripped the fruit-trees in general of 

 their foliage . In France also in 1731 and 1732 that 

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

 (Arctia ph<zorhcea\ whose history has been given by the 

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

 neral 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 

 compel people to collect and destroy them; but this would 

 in a great measure have been ineffectual, had not some 

 cold rains fallen, which so completely annihilated them, 

 that it was difficult to meet with a single individual* 1 . 



a Travels, ii. 6. b Collinson in Philos. Trans, liv. x. 65. 



c Rosel, I. ii. 15. d Reaura. ii. 122. 



