432 APPENDIX I 
yellowish on the sides with a large gray triangle on the second 
segment. Chrysops mitis has the abdomen entirely black, with 
faint triangles of grayish hairs. Chrysops sordidus is distinguished 
by having the first and second segments of the abdomen marked 
with yellow on the sides, and the posterior margins of all the seg- 
ments narrowly bordered with gray, and a dorsal row of small 
triangles. The species are all of about the same size, a little less 
than a half inch in length, C. excitans as a rule being a little larger 
than the other two. ; 
The larger horse-flies are represented by at least six species, 
all belonging to the group with hairy eyes. These were formerly 
separated from the genus Tabanus and placed in the genus Therio- 
plectes, but they are now united, the character used in separating 
them being probably only of subgeneric value. The two most promi- 
nent species are Tabanus flavipes, or the yellow-footed horse-fly, and 
Tabanus zonalis, or banded horse-fly (Pl., Fig. 2). They are nearly 
three-quarters of an inch in length, with wings spreading an inch and 
a quarter; black, with the posterior margins of the abdominal seg- 
ments bordered with a band of golden-yellow hair; the wings are 
brownish, tinged with yellow toward the base. The two species 
closely resemble each other, but can be readily separated by the 
latter’s having the tubercle in front of the base of the wing reddish, 
and the yellow bands of the abdomen broader, with slight ante- 
rior projections on the second and third segments. The Tabanus 
auripilus of northern Europe is closely related to flavipes. Another 
species of about the same size is Tabanus affinis (Pl., Fig. 3); 
it is a dark brownish black, with the sides of the abdomen red. 
The little-headed horse-fly, Tabanus microcephalus, is about one- 
half inch in length; the head is comparatively small, not exceeding 
the width of the thorax; the abdomen is marked with three rows 
of conspicuous grayish triangles. The northern horse-fly, Ta- 
banus septentrionalis, is similar in general appearance, but with a 
larger head and less prominent abdominal markings. The sixth 
species, Tabanus illotus, is distinguished from the preceding one 
by the broad, distinctly excised, third antennal joint, and faint 
brown clouding on the cross-veins. 
The larvee of the horse-flies (Fig. 4) are aquatic or subaquatic, 
living either in the mud in streams and swamps, or in wet earth 
adjacent to springs. The eggs are placed on plants overhanging 
the water or in very wet situations. The eggs hatch in about a 
week, and the young larve drop into the water or mud. The 
larvee are carnivorous, feeding upon other insects and snails, and 
probably repaying to some extent their annoyance when adult. 
They are cylindrical, tapering gradually toward the end, and 
usually translucent, whitish, and in some of the larger species 
