Artitropa reducta Riley, 1925

Cock, Matthew J. W., Congdon, T. Colin E. & Collins, Steve C., 2015, Observations on the Biology of Afrotropical Hesperiidae (Lepidoptera). Part 8. Hesperiinae incertae sedis: Dracaena Feeders, Zootaxa 3985 (3), pp. 301-348 : 320-324

Artitropa reducta Riley, 1925

This species name was first introduced as an aberration (‘ab.’) of A. comus by Aurivillius (1925b) in his account of the Lepidoptera collected on the second German central African Expedition 1910–1911, based on four males from Kimuenza, which is now an area of Kinshasa, DR Congo. Accordingly, this name was not available under the International Code of Zoological Nomenclature, until Riley (1925) almost immediately used it as a subspecies name, thereby validating it with his authorship. As noted above under A. comus, Carcasson (1981) treated reducta as a valid species separate from A. comus , which has been followed by subsequent authors ( Ackery et al. 1995, Larsen 2005). Artitropa reducta is found from Cameroon, DR Congo, east to southern Ethiopia, western Kenya, and south to Zimbabwe, Zambia, Malawi and Mozambique ( Evans 1937, Pringle et al. 1994, Ackery et al. 1995, Heath et al. 2002).

In Kenya this species was only recorded from the Shimba Hills ( Sevastopulo 1974), Teita Hills and Mt. Sagalla ( Larsen 1991), apart from a single suspect Nairobi record ( Riley 1925). Since then it has been recorded from Kakamega Forest as A. comus ( Kühne et al. 2004) and occurs more widely in Kenya west of the Rift Valley (specimens in ABRI). Larsen (pers. comm. 2014) now considers the records from Teita Hills and Mt. Sagalla to be an error. Sevastopulo (1974, unpublished) reared a single specimen which he reported as A. reducta from Kwale, Kenya Coast. We have not been able to examine this specimen, and this record has not been repeated, but we do document his unpublished observations below.

In Tanzania, it is known from a few specimens from Mpanda and Kigoma District in western Tanzania (ABRI collection). There are one or more apparently disjunct populations from further east and south-east in Tanzania, with records from the Udzungwa Mountains, Kihansi (ABRI specimens) and a series reared by TCEC from the Rondo Plateau. These probably represent a distinct subspecies (T.B. Larsen pers. comm. 2014). It seems possible that the single record from Kwale could relate to these populations in which case further populations may well occur on the other Eastern Arc Mountains. A distinctive and stable population on Mt Selinda, eastern Zimbabawe may prove to be a distinct species (T.B. Larsen pers. comm. 2014). Further investigation should clarify whether these are truly disjunct populations, or whether A. reducta is overlooked in extensive parts of its range.

Adult behaviour. Riley (1925), Dickson & Kroon (1978), Carcasson (1981), Pringle et al. (1994) and Heath et al. (2002), all comment that the adults are either active at dusk or crepuscular, and visit flowers when active. For example, at Mount Selinda, Zimbabwe, adults have been seen feeding from the flowers of Brunfelsia (Solanaceae) ( Pringle et al. 1994). Adults rest with their wings closed, and the white markings on the hind wing underside are then very conspicuous ( Figure 17 ).

Food plants. Early food plant records were mostly attributed to A. comus , since A. reducta was considered to be a subspecies. R. Van Someren (in Riley 1925) established that the food plant at Jinja, Uganda, was a Dracaena sp. There are some reared specimens from Jinja in V.G.L. Van Someren’s collection in the BMNH Accessions, but no material to match in the BMNH Dry Early Stages Collection. Le Pelley (1959) listed D. steudneri as a food plant in Uganda (as A. comus ), but this may not have been based on R. Van Someren’s work, as V.G.L. Van Someren reports the food plant of A. comus and subspecies to be D. fragrans (as D. ugandensis , mis-spelt ugandae) (?) and D. mannii (?)—the question marks indicating doubt as to the species identities ( Van Someren 1974). Sevastopulo (1974, unpublished) reared this species from Dracaena mannii (as D. usambarensis ) at coastal Kenya, in 1964. Possibly he reared it more than once, as he refers to ‘a larva’ from Kwale which emerged 23 Nov 1964 in his unpublished account, but to ‘a single larva’ from Makardara Forest, Shimba Hills, which emerged in Dec 1964 in Sevastopulo (1974), but we suspect this is confusion over a single rearing. Dickson & Kroon (1978) report that it breeds on D. mannii (as D. gazensis ) in Zimbabwe. Pringle et al. (1994) also give D. mannii (as D. reflexa var. nitens ) and add D. steudneri ; by implication the records are both for Zimbabwe, although the latter could be based on East African observations. Subsequent authors ( Carcasson 1981, Larsen 1991, Ackery et al. 1995) merely give Dracaena as the food plant.

MJWC has reared A reducta from D. steudneri at Kigale, Rwanda (01/201) and SCC has reared it from D. fragrans and D. steudneri in western Kenya. TCEC collected early stages on D. mannii in Tanzania (Rondo Plateau) and Zambia (Lisombo Stream), and on D. steudneri in northern Malawi, where the plants were an occasional feature of the roadside vegetation on the road down from Mzuzu to Chinteche. Caterpillars from the Rondo Plateau were reared through on D. steudneri at Mufindi, but were reluctant to feed on D. laxissima .

Life history, Uganda. Riley (1925) includes quotes from V.G.L. Van Someren and includes photographs of the caterpillar and pupa. The quote regarding A. reducta (as A. comus ) would seem to be based on the work of R. Van Someren. "The eggs when newly laid are a pink colour and, as development goes on, they turn greyish. They are laid singly. Five to eight days elapse before they hatch. The newly hatched caterpillar is yellowish-green with dark head. With each moult the colour changes to a light greenish-white with yellow head with two black or dark brown spots. They are voracious feeders and like others of this group rest in curled-up leaves, either naturally curled or leaves with edges approximated and attached with silk. The food plant is a species of Dracaena. The caterpillar pupates in a folded leaf and is attached in the usual way, i.e. at the hind end and by a body band. The freshly formed pupa is greenish-white and gradually turns to a dirty pinkish green covered with a white powdery substance. My specimens emerged in three weeks, but in Uganda they emerge rather more quickly. The insect is crepuscular and appear to rest during the day. They are not common.”

Caterpillar, Rwanda. There were five instars in the Rwanda material, the head capsules measuring 1.0 x 1.0, 1.3 x 1.4, 1.7 x 1.9, 2.4 x 2.7 and 4.1 x 4.2 mm wide x high. The adfrontals were not clearly differentiated from the epicranium, and the adfrontal suture was only obvious in the final instar head capsule once it had moulted to the pupal stage. For the first two instars, the head is black; the second instar was noted to have the anal plate uniformly black (90/201B). A third instar caterpillar (90/201A) measured 16mm when newly moulted; head black, with a slightly paler diamond shape in upper part of face; T1 with narrow black pronotum; anal plate brown, speckled with light brown dorsal line. Another individual had the head completely dark (90/201F), and four others had more extensive pale brown markings similar to those of the next instar, but with the edges less sharply defined (90/ 201B–E). Thus, in individual 90/201B the face was brown; the posterior margin broadly dark, extending to the edge of the face; a large spot on each epicranium joined across the upper adfrontals and frons; ventrally and around stemmata darker brown; all borders between markings diffuse.

Newly moulted to instar 4, individual 90/201A measured 19mm; head light brown ground colour; a large black spot on epicranium each side of face, adjacent to outer margin of adfrontals, the dorsal inner margin straight; dorsal part of adfrontals and adjacent frons slightly darker; a dark line through the anterior stemmata; posterior margin broadly and irregularly dark, except minimal at epicranial suture; ventral area of head dark; pronotum dark; body translucent green; anal plate lightly marked on anterior margin with pale dorsal line. Three other individuals were similar in this instar, although the area between the two epicranium spots was darker, and in one this extended down the frons.

One day after moulting to the final, fifth instar, the same individual measured 37mm; head light brown with yellow flush on face; large black spot epicranium each side of face, adjacent to adfrontals; dark line through anterior stemmata; posterior margin hardly darkened except ventrolaterally. T1 with black spot dorsolaterally on pronotum; body dull whitish blue-green, with darker dorsal line; developing yellow male gonads prominent on A5; anal plate concolorous, posterior margin narrowly white; spiracles yellow-brown; legs light brown. The mature caterpillar has wax glands developed ventrally in a continuous mass from A1 to A8. The last three instars took 4–8, 5–8 and 11–13 days respectively. The five instars of the individual reared from ovum (90/201F) took 7, 5, 6, 5, and 13 days to give a total of 36 days, followed by a pupation period of 15 days to give a total life cycle of about 56 days.

Caterpillar, western Kenya. The material reared from D. fragrans and D. steudneri in by SCC in Kakamega Forest and other localities in western Kenya was not described, but photographs ( Figure 19 ) indicate that it is very similar to that documented from Rwanda.

Caterpillar, north-west Zambia. The head markings of this population from D. mannii at Lisombo Stream, north-west Zambia ( Figure 20 ) seem a little heavier than those from the Rondo Plateua, Tanzania ( Figure 21 ), and closer to those shown from Rwanda ( Figure 18 ) and western Kenya ( Figure 19 ).

Caterpillar, Kenya Coast. Sevastopulo (unpublished) includes photographs of the last two instars of a caterpillar from Kwale, coastal Kenya. The photographs of the penultimate instar show that the spots on the head appear to be joined centrally in a broadly rounded V-shape, similar to that noted in one individual of instar 3 from Rwanda, and for the late instars of A. milleri . Unfortunately the photographs of the final instar do not show the face. In his notes, Sevastopulo records for the penultimate instar: ‘Head dull yellow, a black spot placed centrally on each lobe, the median suture blackish’, and that the final instar is ‘very similar to preceding’. The broadly rounded V-shape spot on the head of some third or fourth instar A. reducta is similar to that of A. milleri above, but A. reducta lacks the lateral spot on the head which is normally evident in A. milleri ( Figures 10 , 12 ). This possible difference in the isolated population from the Shimba Hills merits further investigation. The similarity between late instar A. milleri and instar 3 and 4 A. reducta suggests these two species may be relatively close taxonomically.

Caterpillar, Rondo Plateau, Tanzania. The early stages of this population from the Rondo Plateau, south-east Tanzania, reared from D. mannii by TCEC are documented in Figure 21 . The black spots on the head of final instar individuals seem slightly smaller than those from Rwanda, western Kenya and north-west Zambia ( Figures 18–20 ).

Pupa. The pupa ( Figure 22 ) is similar to those of other Artitropa spp., but with no markings, it measures about 30mm long, and takes 15–17 days to complete development ( Rwanda). The cast final instar skin and the lining of the shelter are lightly covered with white waxy powder, but the pupa is barely covered. The spiracles are pale brown and the proboscis sheath projects some 4mm beyond the cremaster tip. There is an area of relatively weak, backward-angled, pale brown setae on the dorsal part of the thorax, but these are well anterior of where the silk girdle supports the pupa (Figure 22.1). Sevastopulo (unpublished) includes photographs and notes for Coastal Kenya as follows: ‘Pupa, in the larval cell, lined with silk and covered by a waxy powder, and with a silken screen spun across the front of the cell. Supported by a girdle and the cremaster. Ivory white, the head, thorax and wing cases slightly greenish, and lightly coated with a white waxy powder. Prothoracic spiracle pale reddish.’ Sevastopulo’s pupa at the Kenya Coast took only 11 days to emerge.

Figures

FIGURE 10. Ova and caterpillar of Artitropa milleri milleri [TCEC]. 1 – 2, ovum; on Dracaena laxissima, Kigogo, Mufindi, Tanzania, 11 Feb 1998: 1, dorsal view; 2, lateral view. 3, ovum, dorsal view with ribs evident; on D. laxissima, Mufindi, Tanzania, undated. 4 – 7, final instar caterpillar: 4 – 5, anterior segments, anterodorsolateral view, on D. steudneri, Mufindi, Tanzania, 4 Jun 2003; 6, anterior segments, anterodorsal view, collected on D. steudneri, Uluguru Mountains, eastern Tanzania, 23 Jan 2004; 7, head, anterior view in leaf shelter on D. laxissima, Misuku Hills, northern Malawi, 22 May 2004.

FIGURE 12. Final instar caterpillar of Artitropa milleri coryndon, collected on Dracaena steudneri, Thika, Kenya. 1 – 2, collected 22 Dec 1988; moulted to final instar 11 Jan 1989; photographed 16 Jan 89; pupated 27 Jan; 88 / 122 E; 1, head, lateral view; 2, head, anterolateral view. 3, anterodorsolateral view; collected 26 Jun 1988; moulted to final instar 12 Jul 1988; photographed 18 Jul, pupated 27 Jul; 88 / 52 B 3.

FIGURE 17. Adults of Artitropa reducta. 1, female underside, Tanzania, 0 1 Jun 2006 [TCEC]; 2, female underside, collected as small caterpillar on D. steudneri, Kigale, Rwanda, emerged and photographed 21 Mar; 90 / 201 A.

FIGURE 18. Final instar caterpillars of Artitropa reducta, collected as small caterpillar on D. steudneri, Kigale, Rwanda, 7 Feb 1990; moulted to final instar 21 Feb; photographed 22 Feb, 37 mm; pupated 4 Mar; 90 / 201 A: 1, dorsolateral view; 2, detail of head, anterolateral view.

FIGURE 19. Final instar caterpillar of Artitropa reducta collected on either Dracaena fragrans or D. steudneri, western Kenya [SCC]. 1, dorsal view, 1 Jan 2004; 2, detail of head, anterior view, 27 Sep 2004.

FIGURE 20. Ovum and caterpillar of Artitropa reducta, collected on Dracaena mannii, Lisombo Stream, north-west Zambia [TCEC]. 1, ovum, dorsal view, 18 Nov 2005; 2, lateral view, 21 May 2000; 3, head and anterior segments, final instar caterpillar, dorsal view; 3 Nov 2004. 4, head, final instar caterpillar, anterior view, 11 May 2000; 5, final instar caterpillar, dorsolateral view, 11 May 2000.

FIGURE 21. Ovum and caterpillars of Artitropa reducta, collected on Dracaena mannii, Rondo Plateau, south-eastern Tanzania [TCEC]. 1, ovum, dorsal view 19 Feb 2001; 2, ovum, lateral view, 19 Feb 2001. 3, final instar, detail of head, anterior view, 9 Feb 2005; 4, detail of head, anterior view, 28 Mar 1998; 5, final instar dorsal view, 9 Feb 2005.

FIGURE 22. Pupa of Artitropa reducta, collected on Dracaena? mannii, Lisombo Stream, north-west Zambia, 30 Apr 2000 [TCEC]. 1, dorsolateral view; 2, dorsal view.