S i
7 2 BRITISH BLOOD-SUCKING FLIES
knees * ; species of Therioplectes make for the crutch of the legs ;
spccies of Ch/ysosojia \^Haematopota\ prefer one's wrists ; whilst Chrysops
species attack the back of one's neck." Jones (1920, p. 7) found that CJirysops
species caused him great inconvenience by biting on the forehead just above
the eyes.
Having observed that Horse-flies frequently seek pools in order to drink,
Portschinsky hit upon the expedient of covering with a thin layer of petroleum
the surface of water in certain lakes and pools in districts infested with the fly.
The experiment was a brilliant success, and the insects were destro3'ed in
enormous numbers, the majority in attempting to drink adhering to the oil,
while others, although they managed to fly awa\-, were subsequently poisoned
or choked by the oil. In a pool little larger than one square yard in area, there
are reputed to have thus been destroyed over two thousand Horse-flies in five
days. In this way, certain localities such as the Park of Pawlowsk near Leningrad
were completely cleared of Tabanidae.
It is interesting to note that no specimens of Haeviatopota came to drink
at the pools, an experience corroborated by Goffe (1935, p. 102). The late Mr.
Hugh Jones, however, was more fortunate in the New Forest in July 1921,
an extremely dry year ; he took males of Hae-)>iatopota pbivialis (pi. 20,
p. 84) in company with those of a number of species of Tabanns and Chrysops,
in the act of drinking at a pool in the bed of a partially dried-up stream
(see Jones, 1922, p. 40}. A layer of petroleum on the surface of the water is
fatal to aquatic Horse-fly larvae, just as it is to those of mosquitoes.
L I F E - H I S T O R Y
A valuable illustrated account, with bibliography, of the life-histories of
all the species of Tabanidae of which accounts have been published, from 1760
to 1916 inclusive, is given by Marchand (1920). The majority of species of
Tabanidae deposit their spindle-shaped whitish eggs, which gradually become
brown or black after laying, closely packed in rounded or flattened masses,
attached to the leaves and stems of rushes, or to other smooth surfaces over
water or wet ground. According to Surcouf (1924, p. 46) : " certain species
oviposit in damp earth, in vegetable mould, in dry glades, rotten wood, and
even sand on the sea-shore." Each egg-mass may contain from 250 to as
many as 500 eggs, neatly deposited in a regular pattern.
After a lapse of a few days, the larvae from an egg-mass deposited over
water hatch simultaneously and fall into the water, where, according to
statements by P. V. Isaac (1924) and other observers in India, they shed their
skins for the first time within half-an-hour. In three Indian species of Tabanus
studied by Isaac the skin was cast seven times during the course of larval life,
while the larva of a fourth species of the same genus was found to moult eight
times, the change to the pupa taking place at the last moult.
Schwardt (1936) describes the life-history of a N. American species,
* Mr. Goffe writes: "The preference of T. mactdicomis for the ankles is also very
noticeable, and a Tabanid there is almost always this species."
BRACHYCKRA—TABANIDAE
Goniops chrysocoma O.S., in which the eggs are laid on the under-surface of
a leaf. The female clings to the leaf in a position covering the eggs and
broods them until they hatch, after which the female dies. Intermittently the
wings are rapidly vibrated, but it is not yet established whether this plays any
part in controlling the temperature. This peculiar habit may perhaps be
compared with the clusters of ovipositing females of the Rhagionid fly Atherix
ibis Fabr., which are sometimes found in this country (see Verrall, 1909,
p. 288).
Horse-fly larvae, which are soft-bodied, whitish grubs with a longitudinally
striated integument sometimes exhibiting dark bands or other markings, are
found in water, earth, sand, or decaying wood. In shape they are cylindrical,
tapering at each end, with a small retractile head, and a body composed of
twelve segments. The head is armed with a pair of powerful recurved mouthhooks
(mandibles) which are used in seizing prey, and are even capable of inflicting
a sharp prick upon the skin of a human hand. Each of the first seven
abdominal segments is encircled near its anterior margin with a ring of fleshy
retractile protuberances (parapodia), of which when fully developed there are
two transverse dorsal, one lateral on each side, and four rounded ventral
ones (Hart, 1895, p. 222 ; Cameron, 1934, pp. 227 et seq.).
Tabanid larvae, except apparently those of the genus Chrysops (see
Stammer's observations on the behaviour and food of larvae of C. caeciitiens L.
in captivity, i->Lfra, p. 79), are carnivorous, preying upon small Crustacea,
beetle and other larvae and pupae, snails (cf. Hart, 1895, p. 221) and worms ;
in captivity, if a number are kept together they usually display marked cannibalistic
tendencies. It is therefore advisable, if a number of Tabanid larvae
are to be bred at once, to keep each larva in a separate vessel. For accounts
of the technique of rearing Horse-fly larvae see Surcouf (1924), Isaac (1924),
Marchand (1920), Cameron (1926, 1934 and 1935), and Schwardt (1936) ;
see also the notes on Haematopotapluvialis below (p. 85).
The winter is passed in the larval stage, which in some cases is even prolonged
into the third year, Surcouf (1924, p. 59), writes : " The duration of
the larval stage varies according to the species, and it also depends upon the
conditions, whether favourable or otherwise to development. Thus in a
former work (' Tabanides d'Afrique,' 1909, p. 9) we mentioned the rearing of
a larva found by E. Roubaud at Meudon on October 3rd, 1905, and presented
to us. This larva pupated on May i6th, 1907, but the pupa died as the result
of an accident. On the other hand, a batch of larvae found by us in the Ursine
pool, near Chaville in the spring of 1914, was left to its fate in a large trough
at the end of July 1914, and in the spring of 191 5 produced a number of adults
ot Tabanus bisignatus Jaenn., T. bromius Linn., and Chrysops caecutiens
Linn. . . .
" Still more recently in the Laboratoire Colonial of the Paris Museum
we have had a batch of a hundred larvae collected in Verrières Wood (Mare à
Chalot) on April 22nd, 1920. The eggs from which these larvae were hatched
must therefore have been laid during the summer, or at least during the autumn
of 1919. Some of them changed into pupae in July 1920, but the majority.