Tripteroides (Tripteroides) powelli (Ludlow)

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 : 130-131

Tripteroides (Tripteroides) powelli (Ludlow)

subspecies escodae Baisas & Ubaldo-Pagayon, 1953 —original combination: Tripteroides (Tripteroides) powelli escodae .

Distribution: Philippines ( Baisas & Ubaldo-Pagayon 1953).

subspecies laffooni Baisas & Ubaldo-Pagayon, 1953 —original combination: Tripteroides (Tripteroides) powelli laffooni .

Distribution: Philippines ( Baisas & Ubaldo-Pagayon 1953).

subspecies mattinglyi Baisas & Ubaldo-Pagayon, 1953 —original combination: Tripteroides (Tripteroides) powelli mattinglyi .

Distribution: Philippines ( Baisas & Ubaldo-Pagayon 1953).

subspecies powelli ( Ludlow, 1909b) —original combination: Uranotaenia powelli . Distribution: Cambodia, Indonesia, Malaysia, People’s Republic of China, Philippines, Thailand, Vietnam ( Wilkerson et al. 2021).

The genus Tripteroides , with species distributed throughout the Australasian and Oriental Regions, has never been the subject of a comprehensive taxonomic revision; consequently, the majority of its species are poorly known. This is particularly true of species of the subgenus Tripteroides , for which the immature stages of only a “small minority” of species have been described in detail and those that are known are currently indistinguishable ( Mattingly 1981).

Tripteroides powelli sensu stricto and the subspecies escodae , laffooni and mattinglyi were all described from different islands of the Philippines, and only the nominotypical form has been recorded in other countries of the Oriental Region (see above). The four forms have been found on various Philippine islands: escodae —Balabac, Jolo, Mindanao and Palawan (type locality) Islands; laffooni — Leyte (type locality), Mindanao and Samar Islands; mattinglyi —Culion (type locality) and Palawan Islands; powelli sensu stricto —widely distributed from Luzon (type locality) to Mindanao ( Baisas & Ubaldo-Pagayon 1953; Basio 1971). Thus, escodae , laffooni and powelli sensu stricto are found on Mindanao and escodae and mattinglyi both occur on Palawan.

The immature stages are known for the four nominal forms, but they have not been studied or described in comparative detail. In fact, there is some doubt concerning the identity of the larva of powelli sensu stricto, as revealed by Baisas & Ubaldo-Pagayon (1953).

The type specimen described by Ludlow, being a female with unknown larva, is not distinguishable from four kinds of powelli now known in the Philippines. Even were its larva known, it could not be separated from the others unless it was the one which had two-branched ventral siphon tufts [seta 1-S]. The other three are alike in larval characters. Brug’s description of powelli larva (1939), based on Dutch East Indian specimens, does not definitely prove that is the kind of larva Ludlow’s type powelli has. By coincidence, however, the materials we have on hand from Luzon Island (type locality) represent only the kind of larvae which has two-branched ventral siphon tufts, the same as that descried by Brug, but at the same time it differs in certain details from the Dutch East Indian form. It is not at all unlikely other forms of powelli may also be found in Luzon Island if more extensive collections are made, in which case it is only by assumption that the type specimen could be regarded as that whose larva has two-branched ventral siphon tufts.

Assuming the specimens reared from larvae that were studied by Baisas & Ubaldo-Pagayon are conspecific with the type female of powelli , it seems the larvae, as well as the pupae, of the four forms recognized by the authors, based albeit on apparent cursory examination of specimens, are indistinguishable. As stated by Baisas & Ubaldo-Pagayon, “Definite differences between [the] subspecies [are] found only in [the] male terminalia [genitalia].”

The anatomical terminology used by Baisas & Ubaldo-Pagayon (1953) and most other authors for structures of the phallosome of the male genitalia of Tripteroides is confusing. References to the phallosome generally apply to features of the aedeagus, which consists of two lateral plates (aedeagal sclerites) that are normally connected in tergal aspect by a narrow submedian tergal bridge, each plate with a variously developed apical sternal process (ventral arm, VA, of Baisas & Ubaldo-Pagayon) and a less distinctively developed median tergal process (dorsal arm, DA, of Baisas & Ubaldo-Pagayon). Considering this clarification, Baisas & Ubaldo-Pagayon distinguished the subspecies of powelli as follows.

Phallosome of mattinglyi is quite distinct from those of others, not only in powelli complex but also from all species in Group B, because its VA is represented only by teeth which arise directly from rim of tube at point where, in other species of Group B, VA arises. Moreover, mattinglyi has a few teeth, of which three or four arise from a small prominence at base (tergal wall) of DA. Laffooni has finer and more (over twelve) teeth at this point, but they arise not from a prominence but directly from wall of DA. Mattinglyi is strikingly similar in phallosome to rozeboomi of Group A. Beyond that, however, there is no other similarity between them. VA in powelli powelli much shorter than that of escodae or mattinglyi . Viewed in whole terminalia [genitalia] mounts VA in powelli powelli may be seen beneath and at about or below middle of DA. This is because VA is only about half length of DA. VA in either escodae or laffooni measures equal or nearly equal length of DA. Because of long VA, and partly because of usual slight upward tilting of organ, the teeth are well exposed beyond apex of DA (see text fig. 2d) in whole mounts; and teeth coarser. Presence of teeth toward base of DA distinguishes laffooni from escodae ; latter does not have any trace of such teeth.

In many species-rich groups of animals, structures of the male genitalia provide better means for distinguishing species than any other morphological characters. Thus, evolution of genital form is thought to be involved in the origin of species. This would seem to be true of species of Tripteroides , which like many species of the genus Culex , and others, are difficult to distinguish except by features of the male genitalia. Based on the distinct differences in the structure of the aedeagal sclerites of the male genitalia and the apparent sympatry on different islands, as well as significant doubts about the identification of specimens of powelli sensu stricto in countries other than the Philippines, we are confident that the four nominal forms, escodae , laffooni , mattinglyi and powelli , are separate species, which further morphological study, coupled with molecular analyses, will corroborate. Based on this conviction, the three subspecies described by Baisas & Ubaldo-Pagayon are hereby formally raised to specific status: Tripteroides (Tripteroides) escodae Baisas & Ubaldo-Pagayon, 1953 ; Tp. (Trp.) laffooni Baisas & Ubaldo-Pagayon, 1953 ; and Tp. (Trp.) mattinglyi Baisas & Ubaldo-Pagayon, 1953 . Tripteroides escodae and Tp. mattinglyi are currently listed as species in the Encyclopedia of Life; Tp. laffooni should be added to the list.