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Leptomyrmex

Leptomyrmex
Leptomyrmex darlingtoni casent0012024 profile 1.jpg
L. darlingtoni worker from Australia
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dolichoderinae
Tribe: Leptomyrmecini
Genus: Leptomyrmex
Mayr, 1862
Type species
Formica erythrocephala
Diversity
28 species

Leptomyrmex, or spider ants, is a genus of ants and a distinctive member of the ant subfamily Dolichoderinae. Commonly known as "spider ants" for their long legs and spider-like movements, these orange and black ants are prominent residents of intact wet forest and sclerophyll habitats throughout their range. The global distribution of this genus is restricted to eastern Australia, New Caledonia and New Guinea, as well as the nearby Indonesian islands of Aru and Seram.

Newly hatched Extatosoma tiaratum stick insects mimic these ants to avoid predation.

Workers of Leptomyrmex can be easily recognized by elongate antennal scapes which surpass the posterior margin of the head by more than one half their length, a medially notched hypostoma, mandibles with 7–15 teeth and 5–12 denticles, and a laterally located anterior tentorial pit.

Queens are known from only seven species. All known macro-Leptomyrmex queens are wingless (ergatoid). They can be differentiated from workers by the presence of ocelli and their larger size, including enlarged mesosoma and gaster. Whereas the workers possess a mesosoma that is smooth in profile, the profile of queens is distinctly impressed at the promesonotal suture and the metanotal groove. Appendages are noticeably stouter. Queens of at least one micro-Leptomyrmex species possess wings.

The species are informally split into two groups: the macro-Leptomyrmex (21 species), and its sister group, the micro-Leptomyrmex (six species). Macro-Leptomyrmex are large, diurnal and many are conspicuously colored in black, orange or bicolorous black and orange. Micro-Leptomyrmex species have been recently described from Australia, and were placed in Leptomyrmex based on mandibular dentition, anterior clypeal margin configuration, elongate scapes and head, cleft medial hypostomal margin, anterior tentorial pit location, keeled fourth gastral sternite and reduced hind tibial spurs. In some cases, scapes are shorter than in the macro species, and in one species (L. ramorniensis) the hypostoma is only weakly notched. All six species are readily distinguished from their larger congeners by their small size (head width < 0.80mm), brown coloration, relatively short dorsal face of the propodeum, angular (not rounded) petiole and gaster lacking lateral compression. All micro species occur in eastern Australian rainforests.


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