i 
DIPTERA. . 59 
St. Fargeau has ascertained that this maneuvering is performed in 
order to intercept and seize the females. The power of vision is appar- 
ently in proportion to the size of the eyes. Dr. Williston says, ‘that 
they can see for a long distance seems certain. On the uninhabited 
plains east of the Rocky Mountains the writer has frequently seen 
them coming from a long distance, attracted by the sight of the horse 
on which he rode.” 
Such of the larvie as are known are either aquatic or live in moist 
earth and are canivorous, hence they may in some degree compensate 
for the bloodthirsty habits of the adult females. But notwithstanding 
the abundance of the insects, very little has been done toward deter- 
mining the early stages of the species. More than a century ago De 
Geer described the larva of the common European species, Tabanus 
bovinus, and up to 1864 this was the only larva of the kind known. In 
that year Mr. Walsh described « tabanid larva (Proc. Best. Soc. Nat. 
Hist., Vol. IX, pp. 302-306), but without obtaining the adult form. In 
1869 Professor Riley bred the same kind of larva to the adult form 
and described the various stages (Second Rep. Mo. State Entom., pp. 
128-132), the insect proving to be Tabanus atratus Fab., which is 
described further on. 
Dr. Williston says: ‘‘The spindle-shaped brown or black eggs are 
found in spherical or flat groups, stuck together, and attached to the 
leaves or stems of grass and other plants; those of the aquatic larve 
are fastened to rushes. The larve are carnivorous; many live in the 
earth, others in water. They are predaceous, often upon snails and 
injurious insects, thus in a measure repaying the agriculturist for the 
molestation they cause him. The young larvee are known to penetrate 
beetles or other larve and remain within them till they have completely 
consumed them, and their enlarged bodies have filled out the skins. 
Thus the larve of Hematopota have been observed feeding upon 
Helops and those of Tabanus upon Noctue.” (Stand. Nat. Hist., Vol. 
Il, p. 417.) 
Quite recently Mr. C. A. Hart has made a notable contribution to 
our knowledge of this subject,'! which will be drawn from in discussing 
the early stages of particular species. 
Authors generally agree that the after effects of the bites of these 
insects are less injurious than those of mosquitoes or buffalo-gnats. 
The painfulness of the bite and the terror inspired by their presence 
is, however, a source of great torment to animals that are almost help- 
less in protecting themselves against them. The puncture they make 
is large, and after the proboscis is withdrawn there is not unfrequently 
au exudation of blood from the wound. This would tend to remove 
any poisonous injection, but since there is rarely any swelling or 
inflammation produced by these bites, it would appear that no poison is 
conveyed upon their piercing organs. Dr. Packard speaks of cattle 
1 Article VI, Vol. IV, Bull. Ill. State Lab Nat. Hist. 
