Allohelea, Kieffer, 1917

Borkent, Art, 2024, The Phylogeny of the Genera of Biting Midges (Diptera: Ceratopogonidae) of the World, Zootaxa 5438 (1), pp. 1-274 : 224-225

Allohelea :

- The hind leg of Allohelea is modified in several unique ways. The hind tibia is as wide or wider than the hind femur and the hind tibia much wider than the foretibia. The feature is unique within the family. In general, Ceratopogonidae have a hind femur that is wider than the hind tibia and the hind tibia is nearly equal or greater in width than foretibia. Female Allohelea have a ratio of the maximum widths of the hind femur/ hind tibia of 0.87–1.07. Other female Ceratopogonidae have a higher ratio, with the lowest present in Brachypogon demeilloni Grogan & Wirth , which has a ratio of 1.10 (and an unusually large hind tibia, distinctive in Brachypogon , with 201 named species and many more unnamed) ( Grogan & Wirth 1993). Other Ceratopogonidae have a minimum of 1.21 ( Austroconops ) or 1.29 ( Ceratoculicoides , Austrohelea ). Another measure of the wide hind tibia of female Allohelea is a ratio of the width of the hind/fore tibiae, which is 2.25–3.00. Fanthamia ornatipennis has wide hind femur and hind tibia (ratio= 1.44) but the hind tibia is markedly larger than the foretibia of this species, with a ratio of 2.44, similar to that of Allohelea but likely independently derived. The next highest value in other Ceratopogonidae is 1.88 ( Afrohelea ). Brachypogon demeilloni has a ratio of 1.43, a reflection that in that species all the tibiae are wide. Allohelea males also have a wide hind tibia compared to that of the hind femur. The males had a ratio of the maximum width of the hind femur/ hind tibia of 0.98–1.15 and a ratio of the hind tibia/ foretibia of 2.11–2.29. This also seems distinctive but measurements of many other male Ceratopogonidae were not taken, other than of those genera thought to possibly be related to Allohelea .

The apices of the hind tarsomeres 1–2 bear a unique combination of thick, stout spines. Tarsomere 1 has 1–2 thick spines, in some with one being somewhat more slender than the other, tarsomere 2 has two thick spines, also in some with one being somewhat more slender than the other. There are some species with thick spines on the apices of tarsomeres 3 and 4 but it is those on the first two tarsomeres that is unique in the family (others may have thin spines). Isthmohelea , a monotypic genus with otherwise robust and spinose adults (spines on the hind tibia, dorsally on the thorax) and previously placed in the Monohelea complex, is somewhat similar to Allohelea in having strong apical spines on the following: one on each of tarsomere 1(a second as part of the palisade setal row) and tarsomere 2 (1), and two on each of tarsomeres 3–4. However, tarsomere 1 of Allohelea is markedly curved basally and short (shorter than the midtarsomere 1 with a ratio of hind/mid tarsomeres 1 of 0.85–0.89), while that of Isthmohelea is straight and long (longer than the midtarsomere 1 with a ratio of hind/mid tarsomeres 1 of 1.10), further suggesting that the two genera are generally independently derived in this feature (there remains a difference in the number of apical spines on tarsomere 2). Boreohelea , previously considered a synonym of Allohelea and discussed further below, has a moderately thick apical spine on each of tarsomeres 1–4 (a second subapical spine on tarsomere 4). There are also a number of other genera with 1–2 slender to moderately thick spines on at least the apices of tarsomeres 1–3 (e.g. Ceratopogon , Ceratoculicoides , Austrohelea , Serromyia , some Monohelea , Downeshelea , some some Parabezzia , Physohelea , number of genera of Johannsenomyiini , number of genera of Palpomyiini ) and the presence of spines alone is clearly homoplastic.

- Male hind leg with a single, elongate claw, with the fore- and midleg claws each having equal claws (similar to that of the female). This feature is nearly unique within the Culicomorpha but is also present in one species of Stilobezzia (Acanthohelea) ( Cazorla & Spinelli 2014) . The males of the species of Stilobezzia (Debenhamia) also have female-like claws, each being a single claw on each leg. Those in Allohelea and Stilobezzia clearly have evolved this feature independently. However, a single claw is also present in some species of Monohelea ( M. impunctatipennis Clastrier , M. boucheti Clastrier , M. hyalipennis Clastrier and an undescribed Monohelea from New Caledonia ( Clastrier 1985b, 1993b, pers. obs.). A further number of new species from New Caledonia determined as Monohelea (each with an aedeagus with a basal loop—character 128) also have a single hind claw (R. Szadziewski, pers. comm.). These Monohelea species may indicate some relationship to Allohelea . Further to this, it is likely that this too is an expression of female sexual characteristics in the male and perhaps relatively easy to acquire.

- Male with bipartite ventral plate, with a more or less quadrate base with a posteromedial notch bearing an apparently articulating, tapering, distal process. This feature is unique within Culicomorpha.