Trichoprosopon digitatum (Rondani)

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 : 129

Trichoprosopon digitatum (Rondani)

subspecies digitatum ( Rondani, 1848) —original combination: Culex digitatus . Distribution: Argentina, Belize, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Lesser Antilles (includes Trinidad and Tobago), Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Venezuela ( Wilkerson et al. 2021).

subspecies townsendi Stone, 1944 —original combination: Trichoprosopon (Trichoprosopon) digitatus var. townsendi (subspecific status by Harbach & Howard 2007). Distribution: Brazil, Lesser Antilles (includes Trinidad and Tobago), Panama ( Wilkerson et al. 2021).

Rondani (1848) described and named Tr. digitatum (as Culex digitatus ) based on one or more females (number not indicated) from an unspecified locality in Brazil (Belkin 1968). The location of the type(s) remains unknown, but the type locality was restricted to the vicinity of Rio de Janeiro (Guanabara) by Belkin et al. (1971). In the absence of type material, Stone (1944) aptly noted that “It cannot be determined whether the type of digitatum possessed scales on the clypeus, but lacking proof to the contrary, it is best to retain the name for the most frequently encountered, unscaled variety [i.e. species of Trichoprosopon ].” Stone then confirmed the synonymy of Tr. nivipes Theobald, 1901c (synonymy originally by Howard et al. 1915), Tr. splendens Lutz, 1904 (in Bourroul, 1904) (synonymy by Lane & Cerqueira 1942) and Joblotia splendens var. subsplendens Martini, 1931b (synonymy by Lane & Cerqueira 1942) with digitatum based on the absence of scales (presence of setae only) on the clypeus of those nominal species. Stone also noted that four females of Tr. wilsoni Ludlow, 1918 in the “ U. S. N. M.” (National Museum of Natural History, Washington, D.C.) bear type labels but neither of those specimens nor others attributable to Ludlow bear the data provided in the original description of the species; thus, it was “not considered possible to select any one as a lectotype.” In the absence of a definite type specimen, Tr. wilsoni has remained a synonym of digitatum ever since the synonymy was established by Dyar (1928). Of particular note, Stone observed that “One of the four females [‘supposed cotype’] has scales intermingled with the hairs [setae] on the clypeus and therefore should be referred to the new variety [ Tr. digitatus var. townsendi ] described in this paper.”

The presence of only setae on the clypeus of digitatum sensu stricto has been recognized by all investigators ( Theobald 1901c, as Tr. nivipes ; Howard et al. 2015, as Joblotia digitatus ; Dyar 1928, as Joblotia digitata ; Senevet & Abonnenc 1939; Stone, 1944; Lane & Cerqueira 1942; Lane 1953; Zavortink et al. 1983). The last authors (Zavortink et al.) defined digitatum as “the only species of Trichoprosopon with 3‒5 (3‒6) pairs of large preapical teeth on the aedeagus, with these teeth becoming progressively larger distad of the smallest basal tooth.... The pupa is the stage next most easily identified, by its normal countershading and the moderately strong to strong, more-orless rigid seta 6-VI and usually also 6-V…. The adult of digitatum can be identified only by the combination of the densely setose clypeus… the presence of setae on the upper calypter of the wing… the presence of a small patch of light scales at the base of the first hindtarsal segment… and the light integument of the mesepimeron and meron. The larva of digitatum is the stage most difficult to identify. It can usually be told by the combination of a strong, long, single or double seta 0-P… a single or double seta 7-P… only a single ventral abdominal seta (12-II) arising from a sclerotized tubercle… and a long seta 6-VI”.

Stone (1944) described “ var. townsendi ” from a type series comprised of the holotype and 17 paratypes (14 females and 3 males): “The holotype and 11 paratypes were collected at Boa Vista, Rio Tapajós, Pará, Brazil …. Four paratypes were reared by Dyar and Shannon at Porto Bello, Panama... along with a number of typical digitatum . One paratypes [sic] is the supposed cotype of Trichoprosopon wilsoni Ludlow , from Ancon, Panama. One paratype was reared at Montserrat, Trinidad … along with many of the typical variety.” Stone did not indicate whether he examined the genitalia of the males or if the larval and pupal exuviae of the reared specimens were available or examined. He simply stated: “This [variety] agrees with typical digitatum in all diagnostic characters save that there are violaceous scales mingled with the hairs [setae] on the sides of the clypeus.” Without mention of the male genitalia and immature stages of townsendi, Lane (1953) reiterated that “The only difference between this variety and the typical form is that there are scales as well as setae on [the] clypeus.”

As noted above for Tr. compressum, Zavortink (1981) recognized Tr. digitatum as a species complex, consisting “of Tr. digitatum and at least two undescribed species.” Zavortink elaborated: “By any measure, Tr. digitatum is the most successful species in the genus Trichoprosopon . It is widespread geographically, occupying the entire range of the genus from Mexico to Ecuador and Argentina. It is diverse ecologically, with the immatures being found in water in bamboo stumps and tree holes, in fallen fruits and nuts, in Heliconia flower bracts, and in fallen leaves and palm spathes. And it is abundant, with about 95% of the specimens of Trichoprosopon that I have examined being this one species. The undescribed species of the complex occur sympatrically with Tr. digitatum , one in the Pacific versant of eastern Panama and Colombia, the other farther south in the Pacific versant of Ecuador. The immatures of only one of the undescribed species are known, and they have been found most often in leaf axils, a habitat not utilized by Tr. digitatum . The differences between Tr. digitatum and the undescribed species whose immatures are known can be used to illustrate the size of the morphological gap separating related sympatric species in this genus.” Zavortink then mentioned differences between Tr. digitatum and the undescribed species—differences in the coloration of the adults and pupae, the aedeagus and cercal setae of the male genitalia, and seta 7-P of the larvae—and emphatically stated: “The nature of the differences between Tr. digitatum and the new species are important to note, because these species are sympatric and their specific distinctness cannot be doubted.” “Even after the separation of two undescribed species, Tr. digitatum remains a variable species and may indeed still be a complex.” Zavortink did not mention townsendi , but the available evidence indicates that this form is also sympatric with the nominotypical form in Panama and Brazil. In view of the unknown immature stages of townsendi and the unique presence of scales on the clypeus in the absence of morphological information for the male genitalia, we suspect that further collections and integrated study will show that townsendi is a separate sympatric species of the Digitatum Complex; henceforth, it is afforded species status: Trichoprosopon townsendi Stone, 1944 . Trichoprosopon townsendi is currently listed as a species in the Encyclopedia of Life.