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Psyche 6:369-371, 1891.

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Psyche. 1892, vol. 6.
Plate 8.
Tersesthes torrens Twns. 9.




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PSYCHE.
AN INTERESTING BLOOD-SUCKING GNAT OF THE FAMILY CHIRONOMIDAE.
BY C- H. TYLER TOWNSEND, LAS CRUCES, N. MEX. While breaking camp the past sum-
mer, on the Continental Divide in
western New Mexico, at a point about
6 miles west of Patterson, in the western part of Socorro county, I noticed a
small gnat in some numbers on the
horses. This was on the morning of
June 2 1st. The gnats were very small
and black, but their abdomens being
distended and swollen with blood gave
them a red appearance. They were
found mostly on the head and face, par-
ticularly around and below the eyes of
the animals. A few specimens were
hurriedly put in alcohol at the time.
The altitude of this place was something over 7000 feet.
Quite recently, while attempting to
determine these gnats, I found at first
some difficulty in satisfying myself as to their family position. I believe now,
however, that they properly belong in
the Chironomidae. In their venation,
they much resemble the section Anare-
tina, provisionally located by Loew and
Osten Sacken in the Cecidomyiidae.
The hind tibiae, however, have distinct
terminal spurs, which is about the only
character that would exclude them from,
that section. In this character, they
would approach the Mycetophilidae,
but the venation (see PI. 8, fig. 2) is so decidedly cecidomyiid in its character
as to preclude this idea. There are
six longitudinal veins, the fifth vein is forked, and the fourth is to the best of my perception also forked ; there are no cross-veins whatever. In their general
aspect, and the consensus of their char- acters, they approach the genus Cerato-
pogon of Meigen ; and also the genus
Oecacta of Poey, which latter was
erected for a small blood-sucking gnat
in Cuba, known to the inhabitants of
that country as "El jejen." The an-
tennae of the present form are 13- jointed ?), and the palpi are only 3-jointed
(see fig. I of plate). While the vena-
tion is more cecidomyiid than that of
Oecacta, the general form of the body,
as well as that of Ceratopogon, is quite the same. The lancets and labium are
much the same in structure. The palpi
are quite similar, except that Oecacta
may be said to have two additional
joints more at the end, and Ceratopogon




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PSYCHE.
[January 1893.
one. There is quite an important dif-
ference between Oecacta and the present
form in the shape of the eyes, which in
the latter are reniform 01- deeply hol-
lowed out on the inside margin, the an-
tennae being set in a cavity partially
enclosed by the excavated orbit. In
this respect it resembles Simulium and
most of the Cecidomyiidae and Chiro-
nomidae. Judging from the plate (see
plate 27 of Poey's Memoirs on the Nat.
Hist. of Cuba, vol. I), Oecacta does
not possess this peculiarity. Cerato-
pogon has the palpi 4-jointed, and the
conformation of the antennae is peculiar, especially in the 8 .
It must be remem-
bered that I have only $ specimens of
the present species, and that the anten- nae ofthe 8 may or may not be differ-
entiated in form.
The present form, with the genera
Ceratopogon (including Heteromyia
Say) and Oeciicta, possibly also Dia-
mesa, differ to quite an extent from the rest of the Chironomidae. As a group,
they nearly approach the Anaretina in
their venation, the present genus
showing the greatest resemblance in
this respect, and differ from the other
Chironomidae by the body and wings
being shorter and stouter, not culicid-
like or elongate and narrowed, as in
Chironomus, Tanypus, et al. The ven-
ation is simpler; and the lancets and
labium are more elongate, and about
equal in length.
The form here figured differs so ob-
viously from those genera already de-
scribed that there seems no question of
the advisability of making it the type of a new genus, which I shall call Ter-
sesthes (Gr. ~ i ~ ~ - ~ o ^ ~ ~ , to become dry or thirsty). Its , characters are as fol- lows :
TERSESTHES nov. gen. $ (see plate 8).
Antennae 13-jointed, set in large circular excavations in the middle
of the head ; first
joint largest, round; second joint more
elongate, smaller, but larger than following joints ; last joint elongate conical ; interme- diate ten joints equal, sub-moniliform, with hairs somewhat shorter than width of joints. Palpi 3-jointed, longer than proboscis, first joint shortest, second joint swollen, third narrow with a terminal whorl of hairs;
proboscis consisting of a lower lip (labium), with the lancets free but usually more or less approximated to its anterior aspect, both of equal length, extended straight downward, about as long as the head, lancets serrate on outer edge at tip. No ocelli. Eyes reniform, rather deeply excavated on inside margin, dichoptic, front averaging one-third width of head. Thorax moderately stout, but not
humped, a little wider than head, longer than wide, without transverse suture, scutel- lum prominent. Abdomen 7-jointed, some-
what elongate, not wider than thorax, first three segments subequal, fourth smaller, three terminal segments narrowed ; ovi-
positor exserted, consisting of two clavate pieces joined laterally on basal half and terminally divergent. Wings moderately
broad, not elongate, hind margin with a
delicate fringe of hairs, surface sparsely clothed with very short microscopic hairs (revealed only with a high objective) ; six longitudinal veins, the first and second approximated, strongest, ending at about one-third the length of wing; third gently curved distally and ending near the wing apex, fourth apparently forked, fifth
distinctly forked, sixth becoming obsolete before fork of fifth ; an apparent rudiment of a seventh vein; no cross-veins, except one



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January 1893.1 PSYCHE. 371
at extreme base of wing which connects the first and sixth veins, marginal vein not extending beyond tip of wing. Legs slender, not dilated, coxae not elongate; hind tibiae spurred, middle and even front tibiae with microscopic spurs ; metatarsi elongate,
second joint of hind tarsi also elongate, of middle tarsi somewhat elongate, of front tarsi scarcely so, penultimate tarsal joint of all the feet shortened, the last and ante- penultimate joints about equal ; no pulvilli. Tersesthes towens n. sp. 9 .-General
color blackish. Eyes dark brown ; antennal excavations cinnamon colored, nearly three times the diameter of first antennal
joint;
front. face, and lancets shining black, the front with four blackish hairs on vertical margin arising from four papillae ; antennae black, clothed with whitish pubescence;
palpi blackish, labium brownish with some whitish pubescence terminally ; occipital orbits with a few black hairs. Thorax and scutellum deep shining black, smooth,
glabrous, except that the thorax has some scattered black hairs anteriorly. Abdomen soft opaque brown, varying- to light brown, in some of the specimens flavous or rufous at base; balsam mount showing two oval
black spots (bodies?) at base of fifth seg- ment; ovipositor brownish. Legs blackish, tarsi brownish, tibiae slightly so. Wings grayish hyaline, with hardly a smoky flavous tinge, the delicate fringe of hind margin somewhat longest on anal angle where it
terminates abruptly; veins pale, except first and second longitudinal veins which are
brown and end in a brown stigma on costal margin (the first vein becomes obsolete just before reaching stigma) ; halteres brownish,' knobs whitish.
Length of body (incl. ovipositor), I 3-5 mm. (empty) to 2 1-5 mm. (abdomen dis-
tended* with blood) ; of wing, I 1-5 mm. Fresh and alcoholic specimens are slightly longer. Described from both dried and alco- holic specimens, and balsam mounts. Six
specimens collected, June 21, on Continental Divide, Socorro county, N. M., 7000 ft. This gnat was
not observed at any other place
than the one above named.
Note.-It should be stated that what I have called the first longitudinal vein is the auxiliary vein of other families. I have been in doubt whether to describe the wing as having five, or six, longitudinal veins, since the first two in the balsam mount show only as the sides of a single vein. Since, however, they appear in the dry wing, with a low power, as two distinct veins, I have so considered them, and have made the drawing of the wing to represent this appearance. Tersesthes torrens Twns. 9.
Fig. I.-Head, front view, showing lancets, labium, palpi, antennae, an tennal excava- tions, and reniform eyes.
Fig. 2.-Wing. (It should be stated that the stigma does not show in the balsam mount as represented in the figure, but there is a slighter, more general infuscation in the region of the first two veins.)
Fig. 3.-Abdomen, dorsal view, showing
ovipositor, two oval black bodies of fifth segment, and a large irregular contained body (mostly in second and third segments), probably the alimentary canal distended with blood.
Fig. 4.-Hind leg, with coxa attached.
Fig. 5.-Middle leg.
Fig. 6.-Front leg.
Figs. 2 to 6 are enlarged on the same scale. Fig. I is still more greatly enlarged. The hair lines accompanying figs. I to 3 show the natural size. The drawings were all made from balsam mounts, and outlined with the camera lucida. The scanty material in my possession prevents the figuring at the
present time of the component pieces which form the lancets.




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