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This is a large, cosmopolitan subfamily
with many genera, only a few of which extend into the deserts. As
a group the formicines do not seem to be as successful in arid habitats
as are the myrmicines. The exception to this generality is Myrmecocystus,
the only formicine genus that is both common and predictably present.
The formicines share with the dolichoderines
a one-segmented petiole. They differ from dolichoderines in that
they possess an acidopore at the gastral apex. In our species this
is a conspicuous, somewhat tubiform, projection, around the periphery
of which is a conspicuous fringe of long hairs (Fig. 19). By means
of this acidopore the ant sprays the primary defensive compound
of the formicine ants, formic acid, an irritant in respiratory systems
and on surface wounds; as an insecticide it is lethal.
The taxonomy of the desert inhabiting
formicines is not especially difficult, if for no other reason than
that there are so few of them. Genera such as Camponotus
are very much in need of revisionary study but our species are few
and reasonably well known. The genus Myrmecocystus has more
species within the study area than any other ant genus, and was
revised by Snelling (1976); the species are now mostly well known.
KEY
TO GENERA OF FORMICINAE
|
| |
Workers
|
|
| 1 |
Antenna twelve-segmented
|
2 |
| -- |
Antenna nine-segmented (Fig. 208) |
Brachymyrmex |
| 2
(1) |
Mesosomal dorsum, in profile, with propodeum distinctly depressed
below level of promesonotum; metanotal impression usually distinct;
antennal socket at or near margin of clypeus |
3 |
| -- |
Propodeum in profile not depressed below level of promesonotum;
metanotal impression absent or very weak; antennal socket well
removed from margin of clypeus (Figs. 214, 216, 218) |
Camponotus |
| 3
(2) |
Maxillary palpi no longer than head, third and fourth segments
not unusually long; psammophore absent |
4 |
| -- |
Maxillary palpi longer than head, third and fourth segments
long; psammophore present but weak (Fig. 5) |
Myrmecocystus |
| 4(3)
|
4(3) Frontal carinae weak, rounded into antennal fossa; ocelli
absent or indistinct; body and appendages with coarse, dark
erect setae (Figs. 226-231) |
Paratrechina
|
| --
|
Frontal
carinae weak, rounded into antennal fossa; ocelli distinct;
body and appendages without coarse, dark erect setae (Figs.
273-275) |
Formica |
| |
|
|
| |
Males
|
|
| 1 |
Antenna 13-segmented; mandible well developed, with masticatory
margin
|
2 |
| -- |
--
Antenna 10-segmented; mandible vestigial, narrow and pointed,
without masticatory margin |
Brachymyrmex |
| 2(1) |
Antennal socket not, or only narrowly, separated from margin
of clypeus
|
3 |
| -- |
Antennal
socket separated from clypeal margin by about one-half its minimum
diameter |
Camponotus
|
| 3(2) |
Maxillary palpi of normal length, fourth segment shorter than
combined lengths of fifth and sixth
|
4 |
| --
|
Maxillary
palpi unusually long, fouth segment longer than combined lengths
of fifth and sixth |
Myrmecocystus |
| 4(3) |
Tibiae and scape with coarse, dark, erect seta-like hairs;
cerci absent
|
Paratrechina |
| --
|
Tibiae and scape without coarse, dark erect hairs; cerci present
|
Formica
|
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