Packard.] THE POPULATION OE AN APPLE TREE. 167 
says that about the first of June the female deposits her 
eggs. The grubs change to chrysalides early in the spring, 
and in New York the beetles appear early in May. 
The Cylindrical Baric Borer , or Tomicus mali , produces a 
disease like fire-blight, causing the bark to shrivel and peel 
off and killing the branches. Dr. Fitch states that young, 
thrifty trees when attacked by this beetle soon after putting 
forth their leaves in the spring suddenly wither as though 
scorched by fire, the bark becoming loosened from the wood, 
and soon after numerous perforations like pin holes appear, 
revealing the secret of the sudden destruction befalling the 
tree. All these bark boring beetles have a common form, 
that of a cylinder squarely docked at the end, looking as 
though they had been made by the inch and then cut up into 
lengths of about a line each. The body is cov- riG< 132 . 
ered over with fine hairs, so that it acts as a 
brush, like those used for cleaning lamp chim¬ 
neys. The end of the body is sometimes scooped 
out like a gouge, so that the little beetle can 
shovel out the dirt from its house in a true Mile¬ 
sian fashion. The use of the hairs undoubtedly 
is seen when the insect lays its eggs. The female Tomic us. 
beetle tunnels a hole in the bark and makes little notches 
at intervals, in which it deposits an egg. On her return, by 
means of the short stiff hairs projecting from her body, she 
brushes the dirt into the little notches, thus covering up and 
protecting her eggs. Figure 132 represents the Tomicus 
xylographies , enlarged several times. This is a timber beetle, 
and there are several allied forms, but all are much like the 
apple bark borer. It seems from the observations of M. 
Perris, as quoted by Dr. Fitch, that the bark boring beetles, 
i.e ., those infesting fruit trees, differ from the timber beetles 
in an interesting peculiarity. In the bark beetles there is 
a division of labor, the males doing most of the work. 
“Ther^ are commonly several males in company with but 
7 
