1912] The Ottawa Naturalist. 113 



many cut them between the hark and the wood, the pupal- 

 chambers being merely an enlargement of the ends of the larval- 

 mines; others form the pupal-chamber by driving the ends of 

 the larval-mines a half inch or less vertically into the wood, 

 some even cutting the distal half of the larval-mines just below 

 the wood surface; and lastly, a very few small species cut almost 

 the entire system of tunnels and mines slightly below and parallel 

 to the surface of the wood. The Twig-beetles cut both tunnels and 

 mines, when the latter are present, through the wood and pith 

 of twigs. Among the Ambrosia-beetles the tunnels are in all 

 species entirely within the wood, but the depth to which they 

 enter varies considerably with the species. In the genera 

 Corthylus, Pterocyclon, Trypodendron and Gnathotricus the 

 eggs are laid in niches along the sides of the tunnels, and the 

 larvae cut very short mines, known as cradles. The species of 

 Platypus lay the eggs free in the tunnels, but the larvae when 

 nearly ready to pupate cut short cradles in which they pupate 

 and remain until mature. In the genus Xyleborus the eggs are 

 laid free within the tunnels, but the larvae cut no cradles, 

 pupating in the primary tunnels. There is thus a fairly well- 

 marked gradation in habit, both as to the depth of the tunnels 

 and mines below the surface and as to the degree of develop- 

 ment of the larval mines. 



The fourth group contains those species not included 

 among the Bark-beetles, Ambrosia-beetles and Twig-beetles. 

 The American species are few in number. Coccotrypes dactyliperda, 

 an imported form, burrows in date seeds; Cryphalus jalappce is 

 found in jalap root; Hypothenemus eruditus burrows in nuts, 

 book-bindings, and other dry substances, as well as in dead 

 twigs of grape and orange; Pityophthorus cbniperda occurs in 

 pine cones; Hylastinus obscurus bores in the roots of clover; 

 and Cactopinus hubbardi in the pith of the giant cactus. 



Enemies of the Scolytidce. 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 larvae belonging to the families Cleridae, Staphy- 

 linidae, Colydiidae, Histeridae 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 small hymenopterous parasites prey upon the larvae and 

 pupae, and have even been bred from the adults. Larvae of large 

 wood-boring beetles, such as Monohammus, destrov the Scolvtid 

 tunnels by their borings and prove serious enemies to the beetles. 



