Spialia dromus Plötz, 1884

Cock, Matthew J. W., 2016, Observations on the biology of Afrotropical Hesperiidae (Lepidoptera) with particular reference to Kenya. Part 10. Pyrginae, Carcharodini, Zootaxa 4173 (4), pp. 301-350 : 323-328

Spialia dromus Plötz, 1884

De Jong (1978) places S. dromus , together with S. wrefordi Evans and S. ploetzi in the dromus group of Spialia . This species was originally described from ‘Congo’ (Plötz 1884) and occurs throughout sub-Saharan Africa except the Cape and Namibia . Higgins (1925) described var. elongata from Makindu, Kenya; it has the spots of the upper side hind wing continued across space 1C (as on the underside). Some specimens, particularly those from the coast, have reduced white spotting on the upper surface.

Adults and caterpillars may be found in a variety of habitats, ranging from open agricultural land to rain forest margins. It is therefore one of the more widespread and frequently encountered species ( Figure 19 ).

Food plant species Location Reference

ssp. mafa

Hibiscus aethiopicus South Africa Murray 1959, Dickson & Kroon 1978, De Jong 1978; Pringle et al. 1994, Henning et al. 1997, Heath et al. 2002, Woodhall 2005 Hermannia spp . South Africa Dickson & Kroon 1978, Pringle et al. 1994, Heath et al. 2002 Hermannia comosa (= camosa) South Africa Murray 1959 1

Hermannia cuneifolia (= pollens) South Africa Murray 1959 1

Hermannia depressa South Africa Pringle et al. 1994, Henning et al. 1997, Woodhall 2005 Hermannia diffusa (= pilosula) South Africa Murray 1959 1

Hermannia incana (= candicamus) South Africa Murray 1959 1

Pavonia sp(p). South Africa Henning et al. 1997, Woodhall 2005 Pavonia burchellii (= macrophylla) South Africa Murray 1959 1, Heath et al. 2002 ssp. higginsi

Hibiscus sp(p). East Africa Sevastopulo 1975

Hibiscus macranthus 2 East Africa Van Someren 1974

Sida sp. East Africa Sevastopulo 1975

S. ovata (?) (= S. grewioides ) East Africa Van Someren 1974

S. rhombifolia East Africa Van Someren 1974

S. tenuicarpa (= S. cuneifolia )3 East Africa Van Someren 1974

1 The layout of the table in Murray (1959) is not as clear as one would like; he appears to use ditto marks to list the food plants as the same as those of S. nanus , i.e. “The same as S. diomus [i.e. S. ferax ]; also Hibiscus aethiopicus L.” but as this is split onto a second line after ‘also’ it could be interpreted as only referring to H. aethiopicus only, rather than including the food plants of S. ferax (as S. diomus ). This seems to have been the interpretation of De Jong (1978), but South African authors seem to have accepted Hermannia spp. and Pavonia spp. based on Murray (1959). 2 This is a valid name in Tropicos (2015), but an unresolved name in The Plant List (2015). Blundell (1987) treats it as a synonym of H. ludwigii , a common upland species in Kenya, 1520–2440m (5000–8000 ft.), and this may well be the species Van Someren (1974) intended.

3See discussion of this name under S. spio .

Food plants. Species of Triumfetta ( Figure 20 ) are consistently recorded as the food plants of S. dromus ( Table 6). Early records of Hermannia spp. (?), Melhania spp. and Waltheria indica do not seem to have been repeated in recent years, and should be considered as needing confirmation. I have found caterpillars on T. rhomboidea in Kenya and Zimbabwe, and T. tomentosa in Kenya . In Feb 2013 T.C.E. Congdon (pers. comm. 2013) found early stages on a Triumfetta sp. in Tanzania and reared an adult through. Although I have collected Spialia spp. caterpillars from Hermannia spp., Melhania spp. and W. indica , I have not found S. dromus on these food plants.

Ovum. Oviposition on T. rhomboidea was observed in the Shimba Hills at about 13:00h, 13 April 1990 (MJWC 90/48). The ovum shown in Figure 20.1 is similar to others of the genus, and to that illustrated by G.C. Clark (in Dickson & Kroon 1978, Plate 14). It was laid on one of the youngest leaves of a 15 cm plant growing in the open beside a path through scrub.

Food plant species Location Reference

Hermannia sp(p). (?) Southern Africa Pinhey 1965, Larsen 2005

Hibiscus sp(p). (?) Southern Africa Pinhey 1949

Melhania spp. (= Malhamia sp.) East Africa Van Someren 1974, Sevastopulo 1974, 1975, Larsen 1991 [East Africa] Henning et al. 1997, Heath et al. 2002, Woodhall 2005

Triumfetta sp(p). East Africa Sevastopulo 1974, 1975, Larsen 1991 Southern Africa Pinhey 1949, Pinhey 1965

Malawi Gifford 1965

Afrotropical Larsen 2005

Triumfetta rhomboidea South Africa Platt 1929, Murray 1959, Dickson & Kroon 1978, Kielland 1990,

Pringle et al. 1994, Heath et al. 2002, Woodhall 2005 Côte d’Ivoire Vuattoux 1999, Larsen 2005

Triumfetta tomentosa South Africa Platt 1929, Murray 1959, Dickson & Kroon 1978, Kielland 1990,

Pringle et al. 1994, Heath et al. 2002, Woodhall 2005

Waltheria sp(p). East Africa Sevastopulo 1975, Larsen 1991

[East Africa] Henning et al. 1997, Larsen 2005, Woodhall 2005

Waltheria indica (= W. americana ) East Africa Van Someren 1974

Leaf shelters. The small caterpillars sometimes form a shelter on a mature leaf by folding up the distal portion of the leaf either side of a main vein to form a shallow groove, the edges of which are drawn together with silk. Small caterpillars will also use one lobe of the small trilobate leaves of T. rhomboidea and draw the edges up to form initially an open tube, but subsequently a closed shelter. They will also cut a flap from the edge of a leaf and fold this over. Medium sized caterpillars make shelters on mature leaves which may be folded either in a flap from the edge or along the mid-rib, and either upwards or downwards. The mature caterpillars may shelter between two leaves held together by silk. The pupal chamber described by Sevastopulo (unpublished) for S. confusa (which I believe to be S. dromus ) was formed in a folded leaf and perforated with many small holes, as is the case with S. ploetzi below.

Caterpillar. The following account is based on material from Kenya, but the early stages from Harare, Zimbabwe ( MJWC 88/25), were not different. The final instar caterpillar (Figure 21.2–3) is 11mm when newly moulted and grows to 17mm or more. Head 2.3 x 2.4mm wide x high (range 2.20–2.47 x 2.31–2.44, n=7); rounded, slightly indent at vertex, with a long narrow neck; black, shiny, irregularly reticulate; two round brown plaques at the dorsal end of each adfrontal; face partially covered with scattered very short, pale, erect, blunt setae, densely aciculate in the basal half; these setae reduced or absent each side of epicranial suture, around the four brown plaques, and two patches anterolaterally one above the other on each epicranium; in ventral part of face the setae are longer, pale, erect, pointed and simple; laterally and dorsally a mixture of (1) short, pale, erect, blunt setae, (2) slightly longer pale, erect, very narrow linear setae, (3) similar black setae, and (4) long, black, twisted linear setae, truncate at apex, up to 0.70mm long and 0.16mm wide; posterior margin with short, pale, erect, pointed, simple setae. T1 marked in black and white (or yellow as in Figure 21.2); a quadrate white dorsal spot in anterior threequarters; similar dorsolateral spot in anterior two-thirds; these white spots show individual variation in size, but are distinct in all material examined; the narrow black area between these two white spots contains an oval brown plaque near the anterior margin; a similar plaque in the lateral black area at the bottom of the pronotum; ventral to pronotum pale; very short pale, erect, simple setae, slightly dilated and blunt at apex, and long, pale, erect, simple setae; legs black. Body pale greenish blue; dorsal line slightly darker; with mixed short and long pale, erect setae, dilated and blunt at apex; legs concolorous; spiracles inconspicuous. The final instar takes 15–19 days.

The penultimate instar is 6mm long when newly moulted and grows to 12mm. Head similar to that of final instar; 1.5 x 1.6mm wide x high (range 1.44–1.62 x 1.46–1.64, n=4); black, shiny, rugose-reticulate; two small brown, round plaques on dorsal part of each adfrontal (one missing in individual MJWC 88/13); setae similar to those of final instar but less dense and less conspicuous, the black twisted linear setae up to 0.44mm long and 0.10mm wide.

The first instar from an observed oviposition event ( MJWC 90/48) had the head 0.46 x 0.44mm wide x high; brown, shiny, finely rugose; white, pale, erect, blunt primary setae only.

Pupa. The pupa ( Figure 22 ) is 12–13mm long and similar to others of the genus; the proboscis projects just beyond the end of the wings; variable in colour: at one extreme, uniformly dark including appendages, and at the other pale brown with the wings and other appendages pale; Figure 22 is intermediate, i.e. dark brown with mostly pale wings; it turns darker during development; pale, erect, simple setae; covered with a slightly blotchy white wax bloom; spiracles A 2 – A 3 partly visible; pale brown oval plaque on subdorsal anterior margin of A 2 – A 3; in one individual ( MJWC 89 /59B) these plaques are positioned just above and anterior to the spiracles; similar plaques ventral to spiracles on A 4 – A 8 (just visible in Figure 22 ), although in some cases those on A 6 – A 8 are smaller or indistinct; spiracle T1 dark brown, with the fibrous top brown and raised at the posterior margin, 0.44 x 0.71 x 0.31mm wide x high x deep (range: 0.38–0.48 x 0.64–0.80 x 0.20–0.40, n=7); other spiracles dark. The pupal stage lasts 15–19 days.

Natural enemies. I recorded none in Kenya, although caterpillars were collected on 14 occasions. Dickson & Kroon (1978, plate 14) record that caterpillars in South Africa are attacked by a Diptera .

Discussion. Although these descriptions and Figure 21 shows that the dorsal plate on T1 has white spots dorsally and dorsolaterally, the caterpillars illustrated by G.C. Clark (in Dickson & Kroon 1978, Plate 14) from South Africa seem to have a plain black T1 dorsal plate. Clark’s illustrations do not appear to show the brown plaques that I have noted on the caterpillar head and pupa abdomen, but are otherwise compatible with my observations. The T1 differences may reflect geographical variation, but the adults of this species are quite variable (De Jong 1978), and this may also be the case for caterpillars, as it is for pupae.

Figures

FIGURE 19. Adults of Spialia dromus, Kenya. 1 – 2, male, collected as caterpillar on Triumfetta rhomboidea, Kakamega, 17 May 1989; adult 16 Jun 1989; MJWC 89 / 45 A. 3, female, Kakamega Forest, 6 Apr 1990; vouchered. 4, female, collected as caterpillar on T. rhomboidea, Malindi, 21 Sep 1989; adult 24 Oct; MJWC 89 / 59 A.

FIGURE 20. Triumfetta spp., food plants of Spialia dromus, Kenya. 1, T. rhomboidea, Malindi 22 Sep 1989. 2, T. tomentosa, Kisumu, 25 Feb 1988; food plant of MJWC 88 / 13.

FIGURE 21. Spialia dromus egg and caterpillar, Kenya. 1, ovum; oviposition observed on Triumfetta rhomboidea Shimba Hills, 13 Apr 1990; MJWC 90 / 48. 2, final instar caterpillar, dorsal view; collected on T. rhomboidea, Kakamega, 17 May 1989; photographed 17 May; pupated 27 May— 4 Jun; 16 mm; MJWC 89 / 45 A. 3, final instar caterpillar, dorsolateral view; collected as penultimate instar as # 2; photographed 14 Jun; died; 17 mm; MJWC 89 / 45 C.

FIGURE 22. Pupa of Spialia dromus, collected as penultimate instar caterpillar on Triumfetta rhomboidea, Makardara Forest, Shimba Hills, 30 Mar 1989; pupated 30 Apr; photographed 2 May; adult 14 May; 12 mm; MJWC 89 / 26. 1, lateral view; 2, ventrolateral view.