COLEOPTERA 545 



The galleries are excavated by the adult beetles. In some species 

 the gallery is started by a single female, in others the males assist the 

 females in this work. The entrances through the bark to the galleries 

 are similar to those made by the bark-beetles and like them are known 

 as "shot-holes." Under favorable conditions colonies may continue 

 their excavations during two or three generations. 



The fungi upon which these beetles feed are carefully cultivated 

 by them. So far as is known, each species of ambrosia-beetle culti- 

 vates only a single species of fungus, and only the most closely allied 

 species have the same food-fungus. The fungus is started by the moth- 

 er-beetle upon a carefully packed bed or layer of chips. It is probable 

 that some conidia are brought for this purpose from the gallery in 

 which the female was developed. The excrement of the larvas is 

 used in some and probably in all the species to form new beds for the 

 propagation of the fungus. 



In those species in which the larvae are reared in separate cradles, 

 "the mother-beetle is constantly in attendance upon her young during 

 the period of their development, and guards them with jealous care. 

 Themouth of each cradle is closed with a plug of the food-fungus, and 

 as fast as this is consumed it is renewed with fresh material. The 

 larvse from time to time perforate this plug and clean out their cells, 

 pushing out the pellets of excrement through the opening. This debris 

 is promptly removed by the mother and the opening again sealed with 

 ambrosia. The young transform to perfect beetles before leaving 

 their cradles and emerging into the galleries." 



A detailed account of the ambrosia-beetles of the United States 

 was published by Hubbard ('97), from which I have drawn largely 

 in the preparation of the account given here. 



While the ambrosia-beetles are chiefly injurious to forest -trees, 

 there are certain species that injure wine and beer casks ; and one 

 species, the pear-blight beetle, Anisandrus pyri, sometimes infests 

 the tips of pear and apple branches, causing an injury that is often 

 mistaken for the bacterial disease known as pear-blight. 



Nearly four hundred species of scolytid beetles, representing 

 many genera, have been described from America north of Mexico. 



