General Habits. 



In habits the Ipidce of our fauna form a sharply isolated group. Their 

 tunnels, cut usually in the bark or wood of trees, are characteristic of the family. 

 Our species present two quite distinctive habits, corresponding to which they 

 have been termed True Bark-beetles and Ambrosia-beetles, respectively. The 

 former, with very few exceptions, cut their tunnels entirely, or almost entirely 

 in the bark or between the bark and the wood; the latter, on the other hand, 

 penetrate the wood and the young develop in the tunnels well below the wood 

 surface, nourished entirely by a peculiar fungus called Ambrosia, which grows 

 invariably upon the tunnel walls and stains them dark brown or black. 



With True Bark-beetles the typical habit is as follows: An entrance tunnel 

 is cut obliquely upward through the bark to the wood surface. From the base 

 or inner end of the entrance tunnel one or two or more egg-tunnels are cut, 

 vertically, transversely, or in a radiate fashion, between the bark and the wood 

 along the wood surface. With many species a small, flat cavity, the nuptial 

 chamber, is excavated at the base of the entrance hole, and from it the egg- 

 tunnels originate. The eggs are laid along the sides of the egg-tunnels, singly 

 in cup-shaped egg-niches, a few together in larger egg-pockets, or many in 

 layers and egg-grooves. The egg-tunnels and entrance hole are uniform in 

 size, slightly larger than the diameter of the beetle, and perfectly cyhndric. 

 The larvae excavate slender mines through the inner bark or between the bark 

 and sapwood, away from the egg-tunnels. The larval mines are filled with 

 excrement and increase gradually in diameter as the larvae grow. With some 

 species the mines are kept regularly spaced, rarely intercrossing unless crowded, 

 and present a regular and pleasing pattern; such are those of Chramesus icorice 

 Lee, (PI. 23, fig. 5) in hickory twigs, and Leperisinus aculeatus Say in ash (PL 5, 

 fig. 8). With other species the larval mines are quite irregular and when 

 numerous reduce the inner bark entirely to powder. The ends of the mines 

 are widened to form a more or less distinct pupal cell, which may lie between 

 the bark and the wood, may be continued into the middle layers of bark, or 

 may be sunken below the wood surface, according to the species habit. The 

 adult beetles finally bore round holes through the bark and escape. The result 

 of this excavation by adults and larvae is a set of egg-tunnels and larval-mines, 

 characteristic of the family, frequently of the genus, and commonly of the 

 individual species. 



The tunnels of the ambrosia-beetles are discussed briefly on the following 

 pages. They will not be confused with those cut by any other beetles of our 

 fauna. A distinctive character is the blackening of the tunnel walls by the 

 ambrosia fungus. The larval tunnels of Hylecoetus are somewhat similar and 

 are also lined with a fungus, but they are not similarly discoloured. The tunnels 

 of Stenocelis might be mistaken for those of ambrosia-beetles, but there is 

 no staining from fungi, and the larvae tunnel freely in the wood. 



Aberrant Habits. 



The tunnels of a few of our species of Pityophthorus, notably ramiperda and 

 puberulus, cut their tunnels through the pith of pine twigs (PI. 4, fig. 5). 

 Several species of Conophthorus excavate egg-tunnels through the pith of pine 

 cones (PI. 8, fig. 5). Hylastinus ohscurus Marsh, makes normal egg-tunnels 

 in clover roots. A species of Pityophthorus cuts the egg-tunnels immediately 

 below the wood surface of dry maple twigs, and both adults and larvae feed 

 upon the black wood fungi which abound in sapwood of the twigs they select. 

 Exotic species are found in various nuts, date pits, nutmegs, jalap root, and 

 dry twigs. Species of Xylocleptes breed in plants of the gourd family. Several 

 ambrosia-beetles are recorded cutting their tunnels in the staves of wine casks 



