Culiseta (Culiseta) alaskaensis

Culiseta (Culiseta) alaskaensis (Ludlow)

subspecies alaskaensis (Ludlow, 1906) —original combination: Theobaldia alaskaensis. Distribution: Armenia, Austria, Belarus, Canada, Crimean Peninsula, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Hungary, Iran, Ireland, Latvia, Lithuania, Moldova, Mongolia, Netherlands, Norway, Poland, Romania, Russia, Slovakia, Slovenia, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, United States (Wilkerson et al. 2021).

subspecies indica (Edwards, 1920) —original combination: Theobaldia indica (subspecific status by Maslov 1964). Distribution: Armenia, Azerbaijan, Georgia, India, Kazakhstan, Kyrgyzstan, Pakistan, Russia, Tajikistan, Turkmenistan, Ukraine, Uzbekistan (Wilkerson et al. 2021).

Culiseta alaskaensis was described from five females and one male collected at Fort Egbert, Alaska (Ludlow 1906). According to published works, Cs. alaskaensis sensu stricto is a Holarctic species. In the Nearctic Region, it is found in western North America from Colorado to Alaska and across Canada to Newfoundland. In the Palaearctic Region, it occurs in northern Europe southward to the northern slopes of the Alps and eastward to the far east of Siberia. Subspecies indica was originally described as a species based on specimens collected in the hilly and mountainous areas of Haryana State (Ambala) and Himachal Pradesh State (Bakloh and Dalhousie) in the far north of India (Edwards 1920) and was reclassified as a subspecies of alaskaensis by Maslov (1964). Both subspecies are recorded from localities in Armenia, Georgia, Russia and Ukraine. If the identifications are correct, it would appear that the distributions of the two forms overlap, indicating that they may occur in sympatry. However, those countries lie far north of the type locality of indica, which is located on the south side of the Himalaya Mountains, and they are thus likely to be based on misidentified specimens of the typical form. This agrees with the allopatric distributions of the two forms depicted by Maslov (1967, 1989: map, fig. 60). According to Maslov, individuals of the typical form are “Mostly forest mosquitoes found as frequently in the hills as in the plains” whereas individuals of indica “are mosquitoes of the plains in forest-free regions”. Wood et al. (1979) confirmed that the type form “is widely distributed in the boreal forest across northern Europe, the USSR, and northern Canada.”

Maslov (1967, 1989) and Gutsevich et al. (1971, 1974) distinguished the two subspecies as follows. Culiseta alaskaensis sensu stricto is a dark mosquito, integument and scales dark brown or black; dark and pale scaling of tarsi and abdominal terga in strong contrast; wing entirely dark-scaled or with few pale scales on anterior veins, clusters of dark scales distinct; posterior half of abdominal terga entirely dark-scaled. In general, indica is a paler mosquito, integument light brown or ochreous brown, scutum covered with golden-yellowish scales; dark and pale scales of tarsi and abdominal terga not well contrasted; most veins of wing with scattered pale scales, clusters of dark scales indistinct; posterior half of abdominal terga with few scattered pale scales. Maslov (1967, 1989) is the only researcher to distinguish the male genitalia and larvae of the two forms. In the type form, 2 large setae on basal mesal lobe of gonocoxite bent in distal one-third; larva with seta 4-C (postclypeal) 3-branched, very rarely with 4 branches; head and siphon very dark, often almost black. In indica, 2 large setae of basal mesal lobe of gonocoxite bent just beyond mid-length; larval seta 4-C with 3–7 (usually 5 or 6) branches; head and siphon light brown, sometimes yellowish brown.

Qutubuddin (1952) purportedly described and illustrated the larva of indica from Pakistan. Although he received comments on his manuscript from Peter Mattingly in London, there is no doubt the larva he described is that of an undescribed species of the subgenus Allotheobaldia Brolemann, 1919. The larva is very similar to the larva of Cs. longiareolata (Macquart, 1838), the only currently recognized species of the subgenus, but it bears some distinct differences. The following characteristics place the larva in Allotheobaldia: Antenna short, seta 1-A weakly developed; siphon short and stout, not sclerotized at base, siphon index 1.5, pecten comprised of simple spines (one bifid spine is illustrated), setae 1a-S and 2a-S absent; saddle incomplete ventrally, covering dorsal half of segment X; seta 2-X multi-branched, seta 3-X double; ventral brush (seta 4-X) extended anteriorly on ventral midline of segment, with about 9 pairs of setae. The larva was described from exuviae associated with three reared females. Unlike larvae of alaskaensis, the exuviae examined by Qutubuddin were those of larvae collected “from foul-smelling water in an unused masonry well”. “Several adults were, later on, taken from the same place.” It seems that the adults were misidentified and Peter Mattingly, if he saw the illustrations, did not notice that the larva could not be the larva of indica, which does “not differ [substantially] from those of the nominate subspecies” (Gutsevich et al. 1971, 1974). The larva illustrated by Qutubuddin (1952) differs distinctly from the larva of Cs. longiareolata (based on the description of Hopkins 1952) in having setae 5- and 6-C with multiple branches (single in longiareolata), 5-C more or less pectinate with branches arising from a short stout stem; dorsomentum shorter, less acute distally (a straight-sided triangle in longiareolata); some comb scales distinctly asymmetrical (spicules on one side) (evenly fringed in longiareolata); siphon shorter (index about 2 in longiareolata); pecten comprised of 5–7 spines born entirely on the siphon (pecten with 3 or 4 small spines proximal to the base of the siphon and about 9 on the siphon in longiareolata). In contrast, as described and illustrated by Carpenter & LaCasse (1955), Maslov (1967, 1989), Gutsevich et al. (1971, 1974), Wood et al. (1979) and Becker et al. (2020), the larva of alaskaensis bears the following comparable traits: Setae 5- and 6-C fan-like with multiple aciculate branches; dorsomentum short, edges not exactly straight; comb scales elongate and evenly fringed; siphon longer, index 2.5–3.5; pecten comprised of numerous short spines on proximal 0.2 followed by a row of 16–18 filamentous spines extending to about distal 0.25 of the siphon.

Two nominal species, Theobaldia arctica Edwards, 1920 and Culiseta siberiensis Ludlow, 1920, are currently recognized as synonyms of the nominotypical subspecies, and the nominal Theobaldia wassilievi Shingarev, 1927 is a synonym of subspecies indica. Theobaldia arctica was described from a single male collected at Arkhangel (English for Arkhangelsk), located far north of Moscow on the Northern Dvina River where it empties into the White Sea, and Cs. siberiensis was described from 24 females collected at three places, including Verkhne-Udinsk (former name of present-day Ulan-Ude), located southeast of Lake Baikal in south-central Siberia. The type localities of both nominal forms reside within the distribution of alaskaensis sensu stricto (Maslov 1967, 1989), and both have been listed as synonyms of the type form since Edwards (1921d). In fact, when Edwards (1920) described arctica, he stated that “In coloration and genital structure this insect agrees almost entirely with T. alaskaensis, Ludlow, and may in fact be the same.”

Theobaldia wassilievi was recognized as a distinct species until Martini (1930) treated it as a variety of alaskaensis and Stackelberg (1937) later treated it as a subspecies. Contrary to Knight & Stone (1977), Harbach (2018) and Wilkerson et al. (2021), wassilievi was placed in synonymy with indica (when it was still recognized as a species) by Edwards (1932a), not by Maslov (1967, 1989). Theobaldia wassilievi was originally described as a species from Turkestan, a city in the Kazakh Desert in the southernmost region of Kazakhstan. Turkestan lies at the northern limit of the distribution of indica mapped by Maslov (1967, 1989). Theobaldia wassilievi should therefore remain a synonym of indica.

Based on the available morphological, ecological and distributional information, it seems prudent to recognize indica as a separate species: Culiseta (Culiseta) indica (Edwards, 1920) . Culiseta indica is currently listed as a species in the Encyclopedia of Life. Based on the wide distribution of Cx. alaskaensis, we think it is likely that molecular data will show it is a complex of species.