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 SUBFAMILY DOLICHODERINAE


     The subfamily Dolichoderinae is best represented in tropical areas, where there are many genera and species. Relatively few have penetrated into temperate zones and fewer still into the arid desert. The species which do occur in our area include two which are present only marginally, one introduced species and several wide-ranging forms tolerant of diverse conditions.
      Dolichoderines share with the subfamily Formicinae a one-segmented petiole. The most conspicuous morphological difference between the two groups is the presence of an acidopore among the formicines. Instead of an acidopore, the dolichoderines possess only an anal slit. Both groups lack a sting so defense of colonies and individuals must rely upon other deterrent methods. These two subfamilies employ chemical defenses. Formicines, as a whole, utilize a chemical defense which is partially, or entirely, formic acid. Female castes of our species of formicines will, when their gasters are crushed, yield the characteristic sharp odor of formic acid.
      In the dolichoderine ants the compounds of defense are centered around cyclopentanoid monoterpenes. These compounds are quite aromatic and, to humans anyway, very disagreeable. The odor has been variously compared to rancid butter, rotting coconuts and scorched rubber. Whatever the comparison, these compounds are convincingly repugnant and provide an excellent field identification characteristic.
     Colonies of Liometopum, Tapinoma, and Forelius are usually quite large and numerous females are present. Those of Dorymyrmex are evidently smaller and may have only a single female. With the exception of Tapinoma, however, none of these has been extensively studied. The dolichoderines as a group are quite aggressive omnivores. Forelius, Liometopum, and Forelius are all trail foragers. In Dorymyrmex trails are less consistent and when they do occur, do not receive the heavy traffic so characteristic of the others.
      Since our fauna includes so few species of Dolichoderinae, the following keys are for both genera and species, except that in the key to males no effort is made to separate those of the two Forelius species or the three Dorymyrmex.

KEY TO GENERA AND SPECIES OF DOLICHODERINAE
workers & queens
1 Juncture of basal and posterior faces of worker propodeum rounded, not produced upward as a conical process in lateral view (Figs. 196, 198, 200); segment 3 of maxillary palpus distinctly shorter than following three combined


2
-- Juncture of basal and posterior faces of worker propodeum, in profile, conically produced upward (Fig. 202); segment 3 of maxillary palpus longer than following three combined (Fig. 6) (Dorymyrmex)


6
2 (1) Worker monomorphic; gastral terga without appressed dense, long grayish pubescence; gap between lateral margin of clypeus and base of mandible very narrow (Fig. 195a)

3
-- Worker polymorphic; gastral terga with appressed dense, long grayish pubescence; gap between lateral margin of clypeus and mandibular base large (Fig. 191a)

Liometopum occidentale Wheeler
3 (2) Frons and dorsum of mesosoma with at least several long erect setae; petiolar scale small, distinct, erect or suberect (Figs. 198, 200)

4
-- Frons and dorsum of mesosoma without erect setae; petiolar scale small, strongly inclined forward, adnate to anterior peduncle (Fig. 196)
Tapinoma sessile (Say)
4(3) Ventral margin of clypeus thin, without median beveled area; mandible with four distinct, close teeth and a weak basal tooth, denticles present only between basal and subbasal teeth; worker metanotum not depressed below base of propodeum, latter flat (Forelius)




5

--�������� Ventral margin of clypeus thick, with median, triangular beveled area; mandible with four or five widely spaced teeth, with several minute denticles between each (except apical and preapical teeth); metanotum of worker sharply depressed below level of anterior margin of propodeal base, latter strongly convex


Linepithema humile (Mayr)
5 (4) 5(4) Antennal scape and all tibiae with at least a few suberect to erect hairs; vertex corner with a few short erect hairs; worker pronotum with 6 or more erect hairs (Figs. 198, 199)

F. mccooki (Forel)
-- -- Scape, tibiae and vertex corner without erect hairs; worker pronotum with 2 or 4 erect hairs (Figs. 200, 201)
F. analis (André)
6(1) Head, mesosoma and gaster concolorous, from yellowish to blackish brown. Worker: interocular distance less than 1.5 times EL; CI less than 95 (Fig. 204)

7
-- Head and mesosoma ferruginous, gaster brownish black. Worker: interocular distance more than 1.5 time EL; CI over 95 (Fig. 203)
D. bicolor Wheeler
7(6) Mesonotum, in profile, distinctly broadly angulate at about posterior two-thirds so that there are two distinct surfaces (Figs. 00, 00)
8
-- Mesonotal profile more or less evenly curved and without angulation posteriorly (Figs. 00, 00)
9
8(7)
Color light to very dark brownish, head and gaster commonly darker than mesosoma; pronotal seta pair usually present

D. insanus (Buckley)
-- Color clear yellowish to reddish yellow, often with vertex, mesosomal dorsum, and apex of gaster infuscated; pronotal seta pair commonly absent

D. flavus McCook
9(7) Mesonotum weakly curved in profile (Fig. 00); eyes exceptionally large, IOR ca. 115; head and gaster brown, distinctly darker than mesosoma

D. species 2
-- Mesosoma strongly convex in profile (Fig. 00); eyes not exceptionally large, IOR ca. 128; head and mesosoma concolorous yellowish red, gaster mostly dull brownish

D. species1
 
Males
 
1 Scape much longer than second flagellar segment (Figs. 197, 205) 2
-- -- Second flagellar segment distinctly longer than scape Linepithema humile (Mayr)
2(1) Segment 3 maxillary palpus about as long as second, much shorter than combined lengths of last three; head flattened in profile or not

3
-- Segment 3 of maxillary palpus much longer than second, about equal to combined lengths of last three; head distinctly flattened in profile (Fig. 205)

Dorymyrmex spp.
3(2) Scape shorter than combined lengths of next four segments; base of gaster without impressed area for reception of petiole; erect body hairs often abundant

4
-- Scape about as long as combined lengths of next five segments (fig. 197); base of gaster with impressed area for reception of petiole; erect body hairs sparse

Tapinoma sessile (Say)
4(3) Head distinctly flattened, more or less concave beneath; body hairs sparse; length less than 4 mm
Forelius spp.
-- Head convex anteriorly and posteriorly (Fig. 194); body hairs abundant; length 7-11 mm
Liometopum occidentale Wheeler

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Date of this version 18, October 2003
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