48 Disease and Death of Trees — Generalities 
to dry up, and even large branches and entire trees can be 
killed by these scale-insects if they are abundant. 
A very large number of insects coming from several of 
the various orders, inhabit the foliage and smaller twigs in 
their egg and larval stage and produce what is known as 
galls, peculiar swellings, tumors, or malformations, often 
highly colored. Especially the family of gall-fies, number- 
ing some hundreds of species, inhabit largely the oaks, 
producing all sorts of leaf-galls. Among these are the galls of 
commerce from which ink and gallic acid are manufactured. 
The damage is too small to deserve much attention, but 
where excessive, the leaves should be gathered while green 
and burned, to get rid of the deformation. 
These swellings or malformations of twigs, buds and shoots 
are often accompanied by a shortening of the annual growth 
and a crowding of the foliage, forming what is known on 
willows as the “willow rosette’? and on pines or on spruces 
as the “pine-apple.”’ 
The saw-flies, similar to the gall-flies, lay their eggs in 
the tissues of the leaf, but as they live in colonies and have 
often two broods in a season and their larvee feed voraciously, 
they are more injurious than the gall-flies and may, as in the 
case of the larch and the pine saw-flies, cause widespread 
havoc. The conifers suffer especially from these pests. 
With the family of beetles known as weevils we come to 
the stem-boring insects. For, although some feed on the 
foliage and puncture the bark, their worms or grubs inhabit 
not only the fruit but also the young twigs; the beetle 
with its long cylindrical snout perforating the bark and 
depositing an egg in the hole, the larva developing from it, 
burrowing beneath the bark, loosening it from the wood or 
boring into the stem and destroying the wood. 
Bark-beetles, the “grubs” of which live under the bark, 
