44 
OBSERVATIONS IN NATURAL HISTORY. 
seen no more, but at the same time gives the 
alarm to others, and causes a general deser- 
tion of the locality we are traversing." — Pp. 
40—42. 
With regard to the body of the work it 
confirms a large collection of facts without 
any particular order. These facts are for the 
most part of a nature to be hardly called com- 
mon. They have some novelty or singularity 
about them. Many are valuable, as indeed 
all facts are when just published. Some of 
these are interesting to all classes, others are 
valuable to a particular class. There is no 
general history of anything. We select two or 
three instances which are as good asa thousand. 
" Aphides.— Oct. 3d, 1822.— This morn- 
ing on rising we. found the air completely 
choked with Aphides. The steps at the 
house-door, and even the very walls, were 
black with them. On walking out, myriads 
alighted upon one's clothes ; and getting also 
into one's eyes, ears, and nose, proved an into- 
lerable nuisance. In the middle of the day I 
took a circuit of about three or four miles from 
home, but found the quantities of these insects 
the same wherever I went. A friend, too, 
who arrived from Cambridge, distant about 
eight miles off, assured us tliat they were in 
equal plenty there. Where could these prodi- 
gious multitudes come from, and whither 
were they directing their flight ? Such ques- 
tions are easier asked than answered. It is 
worth noting that the day was particularly 
mild and calm for the time of year, and had 
begun with a fast mizzling rain, which lasted 
for a considerable part of the morning. At 
4 p.m. the thermometer was as high as 64°. 
The wind was easterly, and had blown stea- 
dily from that quarter for three or four days 
previous."— P. 283. 
"Red Spider. — In the summer of 1844, 
the gardener at Bottisham Hall directed my 
attention to a peach-tree infested with the 
red spider. The tree had a very diseased 
appearance ; the leaves were red and spotted 
on their upper surface, and fell prematurely, 
stimulating the tree to put forth new leaves 
from the next year's buds, and so subjecting 
it to great exhaustion. On examining the 
leaves through a microscope, they were found 
to be infested with a very minute mite, scarcely 
bigger than the point of a pin, of an oblong- 
oval form, with eight legs of not very dispro- 
portionate lengths, but the anterior pair a 
little the longest ; the body of a yellowish- 
orange-colour, some specimens redder than 
others, and some with an oblong dark spot 
on each side of the abdomen ; the legs pale 
whitish, and transparent ; two eyes, one on 
each side of the anterior part of the body, 
forming a bright red spot. These mites were 
in all stages of growth, and had evidently j 
been bred upon the leaves. The young were 
more pale-coloured than the adult, which 
were often deep red ; the former were also 
much more bristly than the latter, the hairs 
seeming to wear off with age. Here and 
there might be discerned (more especially on 
the young leaves that were prematurely 
forced, as above mentioned,) clusters of minute 
globules that appeared to be eggs. There 
were also, on the tree, great numbers of 
aphides, which appeared to have had some 
share in bringing it into its diseased state ; 
and also a few of the larva? of what was sup- 
posed to be a Hemerobius, preying upon both 
mites and aphides, empty skins of which were 
scattered everywhere upon the leaves. This 
mite is no doubt the Acarus telarius of Lin- 
naeus, so called from a thin filmy web which 
it spins, and with which it mats the under 
side of the leaves of the trees it frequents. 
Such a web I discovered upon the leaves in 
question ; but the threads of which it is com- 
posed are so extremely fine, that, when single, 
they can be with difficulty perceived, except 
under a high power of the microscope. The 
web alone must injure the health of the leaves, 
independent of the punctures made by the 
mites themselves, which last were distinctly 
seen in some instances inclining forward the 
anterior extremity of their bodies, and plung- 
ing their rostrum into the leaf to feed. The 
mites run upon the threads of their web like 
spiders, but not very swiftly ; off the threads 
their motions seem impeded, and upon a 
smooth surface like glass it is with some diffi- 
culty they move at all. When once a tree 
has become much infested with this parasite, 
its cure is next to hopeless. In the present 
instance, the tree had shown the disease year 
after year ; and there was nothing to be done, 
as I was told, but to cut it down, which has since 
been effected. Some have recommended fre- 
quent sprinklings with cold water, at least for 
plants in hot-houses, which are often attacked 
by these insects ; but this i-emedy is not a 
certain one, nor to be relied on as permanent 
in its effects. In the case of fruit-trees labour- 
ing under this disease, the leaves are con- 
stantly falling, and carrying with them to the 
ground numbers of the mites, which either 
ascend the tree again, or, if it be late in the 
season, harbour under stones, &c, near its 
foot, till the ensuing spring." — Pp. 293 — 295. 
" Extraordinary smarm of flies. — During 
the month of September, in the year 1831, a 
small dipterous insect, belonging to Meigen's 
genus Chlorops, and nearly allied to, if not 
identical with, his C. lata, appeared suddenly 
in such immense quantities in one of the 
upper rooms of the Provost's Lodge, in King's 
College, Cambridge, as almost to exceed be- 
lief. The same species of fly, or one closely 
