62 
THE SCOLYTID BEETLES. 
gating habit of the beetles was observed by Mr. W. F. Fiske, who 
found great numbers congregated under the loose flakes of bark of 
healthy trees just before their simultaneous entrance into the living 
inner bark. Another peculiar habit of the beetles is that of migrat- 
ing from one locality or group of trees where the broods developed 
to another locality or group of trees some distance away, instead of 
continuing their attack on the trees immediately surrounding those 
Fig. 23.— The southern pine beetle: Old egg 
galleries in living tree, with surrounding 
callus of new wood. (Author's illustration.) 
Fig. 24.— The southern pine beetle. 
Egg gallery in living tree marked 
on surface of wood six years before 
block Avas cut from tree: a, Mark 
of gallery on original surface; b, 
resinous wood; e, surface scar six 
years later; d, original surface or 
7-year-old annual layer of wood; e, 
<\x subsequent annual layers of 
wood formed over original wound. 
Author's illustration.) 
from which they emerge. Apparently 
there are rare exceptions to this rule. 
While this species will breed in injured 
and felled trees, it shows a decided prefer- 
ence for those living and healthy, whenever 
it occurs in sufficient numbers to attack and kill them. Its broods 
of larva? must have living, or at least partially living, bark in which 
to complete their rapid normal development. It attacks the bark on 
the middle or upper trunk of medium to large pine and spruce trees, 
and usually selects the largest and best trees first. After the larger 
trees are killed the middle to lower trunk of the smaller trees may 
be attacked. The habit of attack and methods of excavating gal- 
leries are similar to those of the smaller western and Mexican spe- 
