254 THE CANADIAN ENTOMOLOGIST. 



bark and wood, and in some cases apparently upon buds and young 

 shoots. Some engrave the wood surface as do the Bark-beetles ; some 

 have in addition deep chambers within the wood ; and with others the 

 primary" tunnel is cut through the pith itself. With some species the eggs 

 are laid free in the primary tunnels, and the larvae either feed upon the 

 tunnel walls or cut longer or shorter mines through the wood. Several 

 species of this group have a very close relation to a fungus always found 

 in their tunnels. 



A summary of the burrowing habits of these first three groups brings 

 out some interesting relations. Among the Bark-beetles the eggs are 

 usually laid in niches along the sides of the primary tunnels, and the larval 

 mines are usually well-developed. A few species cut their tunnels and 

 mines entirely in the bark ; many cut them between the bark 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 Corthyhis, 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 larvre 

 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 both as to the depth of the 

 tunnels and mines below the surface and as to the degree of development 

 of the larval mines. 



The fourth group contains those species not included among the 

 Bark-beetles, Ambrosia-beetles and Twig-beeiles. The American species 

 are few in number. Coccotrypes dadyliperda, an imported form, burrows 

 in date seeds ; Cryphalns jalappa. 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, and the young leaves of sugar-cane ; 

 FityoplitJiotus coniperda occurs in pine cones ; Xy/eboriis sacchari s.n3.ck?, 



