SAW-FLIES. 
mons; and when the caterpillars are young, or 
immediately after changing their skin, they 
are destroyed in great numbers by continued 
cold and wet weather, or hoar frost during the 
night, Among their other natural enemies may 
also be mentioned insectivorous birds, particularly 
the tribe of woodpeckers, which, however, are too 
scarce in our Scottish woods to be of much ser- 
vice. Mice and squirrels feed upon the pupe, 
and in some cases have been known to destroy 
great numbers of them. After having been 
made acquainted with the appearance of the flies, 
boys might be employed with much advantage to 
catch them when they first begin to appear, 
using for this purpose a small bag-net made of 
gauze. The flies are at no time very active, and 
when employed in oviposition, they are so en- 
grossed with their occupation, that they may be 
approached and secured without much difficulty. 
When the caterpillars abound ona branch, many 
of them may be brought to the ground by sud- 
denly shaking it, or, what would be still more 
effectual, striking it smartly with a pole; they 
ean then be destroyed by trampling upon them, 
or if a large sheet be previously spread beneath 
the tree, collected and otherwise disposed of. 
The best time for doing this is early in the morn- 
ing after a cold night, as the caterpillars are 
then somewhat stiff and inactive, and therefore 
much more easily displaced. When they have 
| prevailed for a time, and numbers have disap- 
peared, it may be presumed that they have en- 
tered upon the pupa state; and if the moss 
and withered foliage be collected from the stems 
and roots of the trees and burnt, many will thus 
be destroyed. It is important also to examine 
the crevices of the bark, where many take up 
their abode; and Kollar recommends that the 
_ stem should be covered with sand a foot and a 
half high, and as broad, on the ground ; as the 
larve and pupe thus will not easily escape 
from the chinks, particularly in old trunks, where 
the bark is very hard, but must be stifled in the 
sand, and those saw-flies that are developed can- 
not make their way out of the sand into the open 
air.” 
The pear-tree saw-fly, Selandria ethiops, called 
by Linneus Tenthredo cerast, produces the well- 
known slimy grub of the pear-tree and the fruit 
trees. The fly is about 24 lines long; and has 
short nine-jointed antenne, with simple terminal 
joints,—a short, broad, black, and shining body,— 
and thin and somewhat hyaline wings with black 
nervures, and with two marginal and four sub- 
marginal cells. The larva is always covered 
with a kind of viscid slime; and has a dark 
greenish black colour; and often inflates its 
body and varies its shape; and resembles fre- 
quently a small snail, and sometimes a tadpole. 
It is an almost annual assailant of the foliage of 
orchards, and so riddles and skeletonizes the 
leaves which it attacks as to make them appear 
at a little distance as if they had been scorched 
149 
by lightning. It makes repeated moultings 
among the foliage, and leaves its exuvie in a 
collapsed and contracted state resembling a black 
thread. Some of the methods used for destroy- 
ing caterpillars may be advantageously employed 
against it; and a sprinkling of quicklime, also, 
would adhere closely to its slime, and perhaps 
ultimately kill the larve. 
The saw-flies of the genus Vematus comprise 
nearly forty British species, and attack a wide 
variety of our useful plants. Their antenne are 
nine-jointed, and have the first and the second 
joints short and the third rather longish ; their 
ocelli are three, and form a small triangle on the 
crown of the head; their mandibles are strong 
and acute, and usually have a single tooth on the 
inner edge ; their wings have one marginal and 
four submarginal cells; and all the joints of their 
tarsi are of nearly equal thickness throughout 
their whole length. The larva of one species 
feeds upon the poplar; that of another lives in 
society on the willow; and that of another com- 
mits extensive ravages upon osier plantations. 
But by far the most destructive is the larva of 
Nematus grossularice, which feeds on the goose- 
berry plant, and whose habits and treatment may 
be regarded as sufficiently illustrating those of 
all the rest. The fly of this species or gooseberry 
saw-fly is from 4 to 5 lines long; its head is 
black ; the organs of its mouth are more or less 
yellowish ; its antenne are black above and pale 
yellow below; its thorax is yellow, but with the 
disk more or less marked with black ; its abdo- 
men and its legs are yellow; and its tarsi, and 
sometimes the tips of the two posterior tibia, 
are black. The eggs are deposited on the under- 
surface of the leaves of the gooseberry plant in 
necklace-like rows along the principal nervures ; 
and, in fine weather, are hatched in 7 or 8 days. 
The larva, when full-grown, is about three- 
fourths of an inch long; but usually appears less 
in consequence of carrying its tail curved in- 
wards. Its head is black; its body is glaucous 
or bluish-green, mingled with yellow; and each 
segment is marked with several transverse rows 
of black shining piliferous warts. It makes seve- 
ral moultings, leaves its exuvie on the leaves or 
twigs, and continues altogether as a larva dur- 
ing from 14 to 17 days. The pupa is longer in 
arriving at maturity than the larva; and, when 
it comes into existence late in the season, it con- 
tinues throughout the winter. Two generations 
of larve almost always occur in the year,—the 
one in the beginning of summer, and the other to- 
ward its close ; and often occasional and compa- 
ratively small broods also appear throughout the 
intervening period. The larvee live in associa- 
tions of from about 50 to upwards of 1,000 upon 
a bush; and they consume all the soft portions 
of the foliage, leaving only the footstalks and the 
principal ribs of the leaves. Various methods of 
destroying the larve or of preventing their ap- 
pearance have been recommended. Attacks upon 
