A New Silphid Beetle From A simple Insect—Trap
International Journal of
A NEW SILPHID BEETLE FROM A SIMPLE INSECT-TRAP.
BY A. LEONARD MELANDER
AUSTIN
The curiosity of an investigating ant may sometimes lead it to destruction. During the month of November last, having had occasion to use a large quantity of the common Texas "stinging red ant" (flogonomyrmex barbatus var. molefaciens Buckley) we selected as the easiest and quickest method of capture a novel expedient. A number of four-ounce bottles were sunk in the gravel nest-heap close to the entrance, nearly to the level of the ground, and then were left opened. The ants ready to resent this disturbance immediately hurried up the little embankment to the open bottles and in their precipitous rush fell headlong over the edge, after which they were unable to crawl up the smooth surface of the glass. After the first excitement the ants largely neglected the traps but now and then a passer-by would peer over the edge, doubtless called there by the stridulation of the ants within, and losing its insecure foothold would topple over into the bottle. In the course of our regular visits to these automatic traps we noticed that in the early morning each bottle invariably contained one or more specimens of a small fly that quickly effected its escape at the slightest noise. After several vain attempts the flies were at last secured by simply corking the bottle, and upon
-
Contributions from the Zoological Laboratory of the
University of Texas No. 28.
examination proved to be a form
belonging to the cave-dwelling genus Zeria
(2let]zarotera), Z. ectinata, originally
described by Dr. Loew from this state.
The propensity of this species to seek
a bottle as a substitute for a burrow
opens a new and interesting field for
collecting myrmecophilous and
cavernfrequenting insects. That this fly is
probably a true myrmecophile, habitually
using the burrows of the agricultural ant
as its domicile, is quite possible, and
even probable when we consider that
only the bottles sunk in the ant-nests
yielded specimens, though numerous
bottles had been arranged as control
experiments in the open fields close by,
and moreover even if placed on the
antbed the bottles never contained a fly
when there were no ants within.
Aside from the .eria and the
everpresent 2leodes tricostata, which in its
capacity of scavenger is always found
scurrying over the ant-beds, another
insect was taken in great numbers.
This one, an exceedingly active little
Silphid beetle, is closely related to
2tamathagus parasitus Leconte, another
ant-guest, which has been taken in the
Eastern States in nests of Formica. The
present beetle belongs to the division
Catopomorphus of the genus, but
distinctly differs from its relative in the
approximation of the elytral strigae, and
in its selection of a host of another
subfamily Na biological difference that
must not be underrated.
Although a number of the flies and
beetles were confined in the bottles with
the ants for several days they rested
unharmed, evidently the closest intimacy
existing between the three. The beetles
would run about among the ants or fly
in the bottle wit.h a quick darting
movement, but at no time were the ants
observed to molest either of their guests.
This is interesting especially in the case
of the Leria which has never before been
found associating with ants, and which,
were the ants unfriendly toward it, might
be supposed to have accidently used the
ant-burrow in place of some other
suitable excavation.
Ptomokagus texanus sp. nov.
Length 2.75-3. mm. Form elongate oval,
Mordellid-like, slightly narrowed posteriorly
color dark castaneous, shining, thorax ahnost
piceous. Head, thorax, and elytra uniformly,
closely and finely strigose, the strigae
provided with short closely-placed, uniform,
*In list of the myrmecophilous Coleoptera of Northern
America Mr. I. A. Schwarz in ,89o notices the occurrence
of another Ptomophagus ant-nests but far
aware this species has not yet been described. Zeria
pectinata has previously been found by Mr. H. G.
Hubbard associating with Ptomophagusisus Horn in the upper
burrows of desert rodents in Arizona. (Proc. Ent. Soc.
Wash. IV., p. 362). In this connection may be cited the
finding of Ptomophagus in (Pt. cavernicola
Schwarz), habit further bearing the preceding
observation.
golden yellow pubescence; that of the head
radiating from the vertex, that of the thorax
and elytra directed straight backvards.
Antennae not reaching the hind angles of the
thorax, the first four joints fuscous, moderately
slender, the first and second joints long, joints
six to eleven broader and shorter, pieeous, the
eighth joint two-thirds as long as the ninth,
and not appreciably narrower. Thorax fully
two-thirds as long as the width of its base, the
sides gradually then quickly narrowing in
front, hind angles acute, base feebly but
distinctly bisinuate, the narrow hind margin
more or less castaneous; disc of the thorax
strigose as well as the sides, the strigae
conforming more (...truncated)