Eretmapodites silvestris Ingram & de Meillon

Harbach, Ralph E. & Wilkerson, Richard C., 2023, The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification, Zootaxa 5303 (1), pp. 1-184 : 111-112

Eretmapodites silvestris Ingram & de Meillon

subspecies conchobius Edwards, 1941 —original combination: Eretmapodites silvestris ssp. conchobius . Distribution: Ethiopia, Kenya, Nigeria ( Wilkerson et al. 2021, excluding South Sudan and Sudan).

subspecies silvestris Ingram & de Meillon, 1927 —original combination: Eretmapodites plioleucus . Distribution: Ethiopia, Kenya, Nigeria, Republic of South Africa, South Sudan, Tanzania ( Wilkerson et al. 2021, excluding Sudan).

Eretmapodites has never been the subject of a thorough revisionary study. The genus currently includes 49 formally recognized species ( Harbach 2022b), many of which are poorly known ( Service 1990). The species treated here, and the one that follows, are the only two species of the genus for which subspecies are recognized.

All species of the genus are characterized principally on diagnostic features of the male genitalia. The females are known for 24 species, larvae for 19 species and pupae for 17 species ( Service 1990; Wilkerson et al. 2021). The majority of species are incompletely described and some known life stages have not been illustrated, or only partially.

Eretmapodites silvestris is a member of the Plioleucus Group ( Rickenbach & Eouzan 1970), which includes six other species: brevis Edwards, 1941, ferrarai Rickenbach & Eouzan, 1970, germaini Rickenbach & Eouzan, 1970, lacani Rickenbach & Eouzan, 1970, ravissei Rickenbach & Eouzan, 1970 and tendeiroi da Cunha Ramos, Ribeiro & de Barros Machado, 1992. By odd coincidence, silvestris sensu stricto and subspecies conchobius are the only forms of the group for which the male, female, larva and pupa are known. Only the male is known for the other species, with the exception that the female of Er. tendeiroi is also known ( Service 1990; Wilkerson et al. 2021).

Although the male, female, larva and pupa are known for silvestris sensu stricto and subspecies conchobius , they are incompletely described and illustrated. Ingram & de Meillon (1927) described the female, larva and pupa of silvestris based on specimens reared from larvae taken from leaf axils of a succulent shrub of the genus Dracaena Linnaeus while conducting surveys at Eshowe in present-day KwaZulu-Natal Province of South Africa. In contrast to silvestris, Edwards (1941) described conchobius based on specimens from the coastal area of Kenya:A male from Malindi and “specimens from Simba Hills and Tiwi (near Mombasa)… reared from larvae found in snail-shells in forest, this being a notably different habitat from that of the type form”. Edwards characterized conchobius as differing from silvestris sensu stricto as follows: “Integument of thorax clearer yellow, no darkening even in middle of pleurae beneath the silvery stripe. Median line of yellow scales on scutum either entirely lacking or represented by a short stripe in front of scutellum and a narrow line extending a short distance only from front margin; scales covering most of scutum brownish rather than black and less irregularly distributed. Hind femur with the anteroventral yellow area less extensive, reaching little if at all beyond middle of femur instead of about ¾ of its length.”

A decade later, Hoogstraal & Knight (1951) described specimens they identified as conchobius that were reared from larvae found in the leaf axils of Sansevieria nilotica Baker growing in the vicinity of Torit, a city in present-day South Sudan. They described the adult as being “intermediate between the typical species, silvestris Ingram and de Meillon , and conchobius as described by Edwards (7) [ Edwards 1941, number 7 in the list of References] in that it possesses the medial transverse dark brown pleural (integumental) stripe of the former, and the scutal and hind femoral coloration of the latter. The male genitalia are as in the typical form (7, fig. 73c). The Torit specimens go to the subspecies conchobius in Haddow’s keys (10) [ Haddow 1946], and in van Someren’s (11) [ van Someren 1949] more recent keys.”

Hoogstraal & Knight illustrated the head, thorax and terminal abdominal segments of the presumed larva of conchobius . Ingram & de Meillon (1927) described but did not illustrate the head and thorax of the type specimen of silvestris , making it difficult to draw comparisons with the description provided by Hoogstraal & Knight. From the poor illustrations of the dorsomentum and siphon provided by Ingram & de Meillon, the only clear-cut difference is the length of the siphon, which is “about as broad as it is long” compared to having an index of “1.7–2.0” in specimens examined by Hoogstraal & Knight. Hopkins (1952) reconstructed and illustrated the terminal abdominal segments of the larval exuviae of the type specimen, and noted: “Siphon crushed… (index 1, perhaps about 1½ before crushing)”. In a footnote that followed the brief description of the larva of silvestris provided by Hopkins, P. F. Mattingly made the following observations.

A pelt [exuviae] of ssp. conchobius from Taveta, Kenya, has been sent me by Mrs. E. C. C. van Someren, and Knight and Hoogstraal have a description of further larvae of this sub-species, from Torit, Sudan, in the press (Amer. J. Trop. Med.). I am indebted to Lt.-Cdr. Knight for permission to quote from their MS. The Kenya pelt differs from the only available pelt of the type form in the shape of the comb spines which resemble Haddow’s type 16 of chrysogaster (Fig. 133). The figure of silvestris (Fig. 134) is misleading in this respect since it shows the basal denticles more strongly developed than in fact they are. The Kenya pelt also differs from that of the type form in having more strongly developed secondary denticles on the pecten spines and in having the subventral tuft [seta 1-S] of the siphon trifid instead of bifid. The comb spines of the Sudan form appear to resemble those of the Kenya form fairly closely though with a higher proportion having the median denticle relatively exaggerated. It is not thought that this difference is significant. The pecten spines, as figured, are much simpler than in the Kenya pelt in which they have very numerous secondary denticles both dorsally and ventrally. The subventral seta [1-S] of the siphon is shown as trifid.―P. F. M.

A comparison of the illustration provided by Hopkins with the one provided by Hoogstraal & Knight reveals the following additional differences, which were not noted by Mattingly. In the type of silvestris : Seta 1-VIII long and single (short and multi-branched in “ conchobius ”); seta 5-VIII branched at midlength (single in “ conchobius ”); saddle of segment X large, covering about dorsal half of the segment (small, covering about dorsal third of the segment in “ conchobius ”); anterior seta 4a-X (of ventral brush) long, double (very short, triple in “ conchobius ”); seta 4c-X double, shorter than 4b,d-X (single, probably as long as 4b,d-X in “ conchobius ”); anal papillae distinctly longer than segment X (about as long as segment X in “ conchobius ”).

Edwards (1941) illustrated the male genitalia of silvestris , and provided the following brief description: “Coxite [gonocoxite] with thumb-like basal lobe bearing a few long hairs [setae]; apical lobe unmodified, but bearing three distally-flattened hairs; no scale-tufts. Style [gonostylus] [strongly bent] with one long hair and two short ones, no scales. Proximal claspette bearing a few long simple hairs; distal claspette stout and moderately long, bearing two bent [strongly sigmoid] hairs at its tip and a few simple ones.” Curiously, Jupp’s (1996) illustration of the male genitalia of silvestris from South Africa differs from Edwards’s illustration as follows: Thumb-like lobe of the gonocoxite with four relatively shorter setae; apical lobe without flattened setae; gonostylus only very slightly bent, with four long setae; distal claspette with two relatively smaller wavy setae at the tip.

Edwards (1941) stated that the male genitalia of conchobius ( Kenya) were “exactly as in typical silvestris ”, and Hoogstraal & Knight (1951) also stated that the male genitalia of “ conchobius ” in South Sudan “are as in the typical form”. In view of the differences between the illustrations of Edwards and Jupp (1996) noted above, we suspect the statements of those authors are based on superficial resemblance.

Despite the lack of detailed, comparative anatomical data for all life stages, we believe the morphological and ecological (larval habitat) differences noted above are indicators of a species complex, consisting of at least three or four species, one of which is conchobius . For this reason, we are compelled hereby to elevate conchobius to species rank: Eretmapodites conchobius Edwards, 1941 . Eretmapodites conchobius is currently listed as a species in the Encyclopedia of Life.