TiPULiDa:. INSECTS. CECiDO.'M'ifiA. 
272 
Okdek — D 
An order of two-wingcd insects, constituting one of 
the most extensive groups amongst the Anmdosa. 
Althougl), strictly speaking, they are only two winged, 
yet they have, as it were, two abortive wings behind 
the true pair ; these are commonly called halteres 
or balancers; they are frequently kept in rapid motion, 
whilst the true wings are apparently quiescent, and 
by this rapidity of motion cause a loud piping noise; 
this is particularly observable in the genus Sericomyia. 
Diptera are usually of moderate size, the largest known 
being a species of Acanthomera from Mexico — about 
one inch and three-quarters in length; the majority are, 
how’ever, small insects. 
Individual species are sometimes extremely abundant, 
so much so as in some instances to become a plague 
and a nuisance. Some of the species may be called 
domestic, the house-fly being an example. Flies have 
in all ages attracted observation from the numbers in 
which they sometimes appear, and in othei'S from the 
terror they excite by their w'ell-known power of causing 
the most intense annoyance both to man and animals. 
One of the plagues of Egypt was a “ swarm of flies,” 
probably mosquitoes, which came from the banks of 
the muddy Nile. Flies have no mandibles (jaws), but 
are provided with a proboscis and also several lancet- 
like organs. The common gnat [Culex pipiens) has the 
parts of the mouth produced into a slender rostrum, 
half as long as the insect; the males have beautiful 
plumose antennse. The approach of the gnat is known 
by its shrill hum ; but its alighting on the face or other 
uncovered part of the skin is so light as not to be easily 
perceptible ; it instantly pierces the skin with its fine 
lancets; these, it pushes by degrees quite in to their base, 
and while the creature imbibes its fill, it apparently 
envenoms the wound, which subsequently causes the 
most painful irritation. Records of their appearance 
in immense hosts in particular localities, even in this 
country, are not wanting; thus we are told, that in 17.36 
they appeared at Salisbury in such hosts as to resemble 
columns of smoke; and in 1766, in the mcnth of 
August, they accumulated in incredible numbers at 
Oxford, resembling a black cloud, almost totally inter- 
cepting the beams of the sun. Such appearances are 
not uncommon in Suffolk and Norfolk, as T have been 
informed by residents in those counties ; on such occa- 
sions their torment is beyond description terrible. 
Neither heat nor cold seems to affect these tormentors 
of the human race. In Lapland they swarm in in- 
credible hosts during certain periods of the year; there 
is neither rest nor sleep for the inhabitants, indoors or 
out, unless the body is smeared with some unguent, such 
as grease, tar, or oil. In the eastern part ol the world 
we well know that mosquitoes are a plague by day, and 
a “ terror by night.” Other species, belonging to the 
family Tipulidce, are well known for the loss occasioned 
by their attacks on grain crops. The Cecidoimjia tritici 
(fig. 171) deposits its eggs in the corolla of the young 
wheat plant, in which the larvae are hatched, and by 
their ravages frequently cause a considerable loss, if not 
IPTERA. 
an entire destruction of the crop. In North America 
the ravages of the grain crops at times spread to an 
alarming extent. In Fitch’s “ Report of the noxious 
insects of the state of New York” are detailed accounts 
of their ravages; the larvae of several genera are equally 
destructive. Species of the genus Chlorops have long 
been known seriously to injure crops. Linnaeus men- 
tions one, Chlorops Frit, which infests the heads of 
barley, causing an annual loss of not less than half a 
million of dollars annually in Sweden. The species of 
the genus Chlorops have, as the name indicates, green 
(tCocidoniyia tritici. ZiTlte same, natural size. cTlte cncoon of Uie fiy. 
d Antenna of tiie male. e An ear of wheat attacked by it. 
f A grain of wheat attacked by it. g The American Cliincli Bug. 
eyes, and may be seen frequently on the young heads 
of grain crops in the spring ; but we must lefei the 
reader to the work above alluded to, for a detailed account 
of the enormous loss occasioned to the farmer through 
the destructive agency of these minute depredators. 
No destructive insect belonging to the familj' Diptera 
is better known than the species popularly called Daddy- 
long-legs {Tipvla oleracea). This species, and some of 
its congeners, occasionally prove by their numbeis ex- 
ceedinglj' destructive in the larva state by feeding upon 
the roots of grass, and thereby doing great mischief; 
