CH. XIX.] OBNOXIOUS INSECTS. 267 



of the perfect insects if any should be disclosed, and 

 to retard the drying of the mould, as a certain de- 

 gree of humidity is necessary to favour the develop- 

 ment of the parts of the perfect insect while it is in 

 the nympha state : in the body and larger branches of 

 trees, the moisture is sufficient for this purpose, but 

 in these small branches, v^hich are killed, the moist- 

 ure would be exhaled by the action of the sun and 

 wind, if they remained on the tree, whereas, by their 

 falling, and being placed nearly or quite in contact 

 with the moist earth, their humidity is preserved. 

 It was not precisely with this view that the prepa- 

 red branches were treated as above mentioned ; but 

 the purpose was attained. The vessel was kept in 

 a warm room, the wood was kept moist, and one 

 perfect insect made its appearance in November, 

 and another in December ; but it was supposed that 

 they would not have been disclosed till the spring 

 if the branches had remained abroad. The insect 

 belongs to a tribe called Capricorn beetles, or wood- 

 eaters, and is probably diffused over a large portion 

 of the United States, wherever the oaks, which it 

 prefers, are found. The falling of the branches, 

 with the larvae in them, enables us, though we can- 

 not destroy the species, to check its ravages in some 

 degree. The branches should be collected from the 

 time they begin falling till they cease to fall, and 

 should be carefully burnt. 



The plum and cherry-trees are often disfigured 

 with irregular swellings on the younger branches. 

 The seat of this disease is in the bark. The sap is 

 diverted from its regular course, and is absorbed en- 

 tirely by the bark, which is very much increased in 

 thickness ; the cuticle bursts, the swelling becomes 

 irregular, and is formed into black lumps, with a 

 cracked, uneven, granulated surface. The wood, 

 besides being deprived of its nutriment, is very 

 much compressed, and the branch above the tumour 

 perishes. On taking off a thin slice of the tumour, 



