THE CANADIAN ENTuMOLOUlSl'. 255 



the sugar-cane ; Hylastinus obscurus bores in ihe roots of clover \ and 

 Cactopinus Hubbardi in the pith of the giant cactus. 



Efiemies of the Scolyiidce. — The Scolytids have many natural enemies. 

 They are preyed upon by many predaceous and parasitic insects, by birds, 

 and are frequently attacked by fungous diseases. 



Adults and larvse belonging to the families Cleridas, Staphylinidas, 

 Colydiidse, Histeridas and others enter the burrows and feed upon the eggs, 

 larvae, pupae and adults of the Scolytids. The predaceous larvae often 

 burrow through the larval-mines after the Scolytid larvae, which they finally 

 overtake and devour. Various dipterous larvae feed upon the eggs and 

 younger stages. Many hymenopterous parasites, Braconids, Chalcids and 

 Proctotrypids, prey upon the larvae and pupae, and have even been bred 

 by Dr. Hopkins from the adults, the parasite emerging through a hole cut 

 in the elytra. Larvae of large wood-boring beetles, such as Monohammus, 

 destroy the Scolytid tunnels and prove serious enemies to the beetles. 

 Woodpeckers destroy large numbers of the Bark-beetles, but apparently 

 do little to check their ravages. 



The tunnels, especially of the Timber-beetles, are frequently overrun 

 with various species of mites. The eggs of these mites hatch before the 

 young beetles are ready for their flight, and in this way young and adult 

 mites are carried by the beetles to the new tunnels. At certain times the 

 declivity of the elytra of various species of Ips (Tomicus) will be found 

 covered with minute miles, and Pterocydon mali and P. fasciatuin are 

 frequently almost completely covered with them upon emerging from their 

 tunnels in the spring. 



Fungous diseases are sometimes very injurious. All stages of the 

 insects are frequently found, more particularly in wet weather, filled 

 and covered with the white mycelium of the fungus. In a felled pine log 

 I noticed that hundreds of adult Ij>s phii had died from this cause in less 

 than two weeks. 



Friends of the Scoiytidce. — As these beetles feed mainly upon dying 

 and dead branches and trunks of trees, any cause which tends to weaken 

 or destroy the trees aids the Scolytids in supplying the proper food-plant. 

 Heavy storms, forest fires, other insects, and the destructive work of man, 

 are perhaps the chief of these. 



Economic Importance. — Owing to the destructive habits of many of 

 its members, the family Scolytidae is of considerable economic importance. 

 The injury done by these beetles may take two forms : living trees may 

 be weakened and killed, and standing and felled timber and sawn lumber 

 may be rendered useless for many purposes by the tunnels of the beetles. 



But few Scolytids attack living, healthy trees, although there are a 

 itw species which apparently choose only trees in this condition. The 



