Gretna carmen capra Evans, 1937

Cock, Matthew J. W., Congdon, Colin E. & Collins, Steve C., 2014, Observations on the biology of Afrotropical Hesperiidae (Lepidoptera). Part 6. Hesperiinae incertae sedis: palm feeders, Zootaxa 3831 (1), pp. 1-61 : 32-38

Gretna carmen capra Evans, 1937

The nominate subspecies, carmen Evans , was described from Cameroon and recorded from Zaire ( Evans 1937), but is now known from Côte d’Ivoire, east to the western parts of Kenya, Tanzania and Zambia ( Larsen 2005). Subspecies capra was described from a single male from Rabai-Mombasa ( Evans 1937). Since then it has been found to be widespread on the Kenya coast ( Larsen 1991), and is reported from inland in Tanzania intermittently from the foothills of the Eastern Arc forests to the east coast of Lake Tanganyika, western Tanzania ( Kielland 1990, Ackery et al. 1995, TCEC unpublished) and Zambia ( Heath et al. 2002). It is not clear from the published literature whether the records of both subspecies in western Tanzania and Zambia reflect overlapping populations, or that both subspecies names have been applied to the same populations. In any case, T.B. Larsen (pers. comm. 2013) has suggested that it may be more appropriate to treat G. carmen as a single species without subspecies. He found no genitalia differences between specimens from Cameroun, eastern DR Congo, Burundi, Zambia, and the Kenya Coast.

We note that material from eastern Africa (i.e. Kenya, Tanzania and Zambia) shows quite a lot of variation, but that where a reasonable series is available from one place, e.g. Shiwa Ng’andu (northern Zambia) or the Kenya coast, the underside markings are fairly constant for that locality. In our treatment below, we describe the Kenyan life history in some detail and provide additional information from Tanzania and Zambia.

Adult behaviour. The adults rest with their wings closed ( Figure 28 ). They fly low and quickly, and are difficult to follow by eye because of their nondescript grey-brown colouring which blends in so well. Occasionally they will settle on coconut palm trunks, and can even be caught by hand with a stealthy approach. A female was observed showing ovipositing behaviour around a Roystonea sp. palm at Diani Beach at about 18.00h on 25 Aug 1995 [ MJWC], and TCEC has observed adults flying at dusk rarely .

Food plants. Sevastopulo (1975), Kielland (1990), Larsen (1991) and Heath et al. (2002) list Borassus , Phoenix and Raphia spp. palms as food plants. Sevastopulo may not have reared this species himself (Sevastopulo unpublished), so his records may have been derived from others. If these observations were from the Kenya coast, as seems most likely, the palms in question are most probably B. aethiopum , P. reclinata and R. farinifera (see under Zophopetes dysmephila above). However, MJWC’s experience has been that this subspecies normally feeds on Cocos nucifera at the Kenya coast ( Larsen 1991). MJWC also found caterpillars on an ornamental palm he identified as Roystonea sp. (Diani Beach, 22 Aug 1995, 95/109; Figure 29 ), but noting that in captivity the caterpillars were feeding much more slowly than another collection on C. nucifera , changed the rearing to C. nucifera . At inland sites in Tanzania, TCEC found this species on R. farinifera and Elaeis guineensis (oil palm). At Shiwa Ng’andu, Zambia, Ivan Bampton and TCEC found early stages on R. farinifera . We consider, therefore, that food plant records from Borassus and Phoenix should be treated as unconfirmed and unlikely to be normal food plants.

Larsen (2005) and Vande weghe (2010) treat G. carmen in West Africa and Gabon respectively (with no subspecies) but the food plants that they list are those recorded from eastern Africa; Borassus , Cocos , Phoenix , and Raphia . Thus we have no food plant records that are associated with the ssp. carmen (or the western population of G. carmen , if it were treated as a monotypic).

Ovum. The ovum is slightly more pointed than hemispherical, with a dark spot on the top.

Leaf shelters. I n Kenya, the fourth and fifth instar caterpillars rest in a rolled C. nucifera leaflet, with the edges held together by strands of silk. Pupation is in a similar shelter. TCEC noted in Tanzania that the caterpillars cut and roll the edges of palm leaves to make a shelter from which to feed. They sometimes use the dead, curled ends of leaflets, and are then very hard to find.

Caterpillar. Based on a limited number of observations of the early instars, there seems to be six instars in Kenya. The first instar is 4mm long, white with a black head, 0.8 x 0.6mm wide x high (n=1); it eats the shell of the ovum and three days after hatching moults without further feeding. The second instar is 4.5mm when newly moulted; it has a light brown head, 1.1 x 1.2mm wide x high (n=2), dark centrally and ventrally, and covered with long dark setae, mostly about 0.3mm long, but up to 0.8mm; as it grows, white wax powder develops laterally on the face; the body is light green with a row of eight quadrate, white dorsolateral spots on A2–A10; covered with long pale setae.

In the third instar ( Figure 30.1 ) the head is 1.7 x 1.8mm wide x high (n=1), pale brown, broadly dark along epicranial suture, on adfrontals and frons; T1 matt dull green; body matt dark green dorsally, sharply defined by a broad subdorsal-lateral line of white waxy powder, diffusely defined ventrolaterally; the white waxy line becomes more pronounced during the course of the instar; head and body covered with long pale erect setae.

The head measures 2.4 x 3.0mm wide x high (n=1) in the fourth instar ( Figure 30.2 ); light brown, adfrontals and frons darker; long pale setae up to 1.5mm long, darker in ventral area; white waxy powder spreads over much of the head as the caterpillar grows. The only fifth (penultimate) instar caterpillar for which a description was prepared had head markings rather like those shown in Figure 33.2 from Tanzania; 2.9 x 3.5mm wide x high (n=1); ground colour pale brown; broad dark line with diffuse edges along epicranial suture from vertex to adfrontals, continuing much narrower along dorsal half of adfrontal suture; a contiguous diffuse dark spot on the epicranium adjacent to the top of the adfrontals; dark spot covering dorsal third of frons and adjacent adfrontals; setae minimal on dorsal half of head, but long on ventral half, around 1.2mm, and up to 1.8mm long; a heavy vertical stripe of white waxy powder on epicranium near adfrontals, running from level with top of adfrontals to bottom of frons, interrupted at the level of the bottom of the dark spot in the frons. The head of the final instar of this individual was plain pale brown.

The head of the sixth and final instar caterpillar measures 3.7 x 4.5mm wide x high (range 3.4–3.8 x 4.4–4.7, n=6). In some cases there are black markings on the light brown head ( Figure 31.1 ), but the head is usually plain light brown ( Figure 31.2–3 ). The following description of the final instar is based on individual 88/77D, collected as a penultimate instar at Bamburi Beach, Kenya, moulted to final instar 18 Sep when it was described. Length 33mm; Head oval slightly wider basally; semiprognathous so that dorsal part of head covers T1; light brown with dark line along epicranial suture; dark spot at top of frons in centre of face; stemmata dark; between mouthparts and stemmata a weakly differentiated yellowish bar; head surface matt, very slightly rugose, covered with long, fine white setae, especially ventrolaterally. Body ground colour pale greenish white; narrow pale dorsal line bordered by darker subdorsal line and pale yellow dorsolateral line; body with long, 2mm, fine white setae, especially dense on A9; T1, legs and spiracles concolorous. By 28 Sep, the sides of the head and body, including the pale yellow dorsolateral line were covered with white waxy powder (cf. Figure 32 ), and the caterpillar pupated 2 Oct. The prepupa becomes covered with wax before pupation. One caterpillar was recorded to take 18 days for the fifth instar.

The caterpillars TCEC documented from Tanzania are rather different. An early instar caterpillar from Tukuyu, south-western Tanzania has the head dark with a pale brown anterolateral stripe, unlike any observed in Kenya (compare Figures 33.1 and 30.1 ). The final instar caterpillar from Kigoma Town, western Tanzania ( Figure 33.3 ) lacks the black line along the adfrontal suture seen in the caterpillars from Tukuyu, south-western Tanzania (Figure 33.2,4–5), but both are much more heavily marked than those shown above from coastal Kenya ( Figure 31 ). Furthermore, Figure 33.2 from Kigoma Town indicates yellow interrupted dorsal and dorsolateral lines on the anterior body, whereas one of those from Tukuyu has a solid yellow dorsal line on the anterior abdomen segments ( Figure 33.2 ), while the other has five or six brownish dorsal marks on the abdomen ( Figure 33.4–5 ). More observations are needed to assess the amount of variation in caterpillar markings at each locality.

Pupa. The pupa ( Figure 34 ) is formed in a single rolled leaflet, and supported by a band of several strands of silk around the thorax. The pupa and the inside of the shelter are covered with white waxy powder. Individual 88/ 77C pupated 8 Sep 1988 and was described 18 Sep; 23mm; smoothly contoured, no projections; short fine pale setae dorsally; longer (> 1mm) on head and anterior and posterior third of the eyes; ground colour under translucent cuticle light green; as the pupa develops it turns paler, then brownish, especially the thorax and appendages and the eyes become red; T1 with dark dorsal line; T2 a thick dorsal dash near posterior margin; T3 a faint short dorsal mark; A4–A6 two pairs of transverse dashes each side of slightly darker dorsal line; similar but faint, diffuse marks on A3, A7; spiracle T1 inconspicuous, a short brown vertical line at base of forewing; other spiracles light brown, inconspicuous. The black markings are variable (cf. Figure 34 ). The pupal stage lasts 17 days (range 14–20) .

Natural enemies. At the Kenya coast, mature caterpillars are killed by a gregarious tachinid fly, Palexorista sp. Between four and nine tachinid larvae were observed to pupate within the corpse of the caterpillar in its shelter, and the decomposing remains of the corpse usually mummify around the 6.2 x 2.8mm (n=6; 90/113B) puparia ( Figure 35 ). The flies emerge some 14–15 days later. Field collected puparia may in turn be parasitized by a gregarious eulophid; from one caterpillar with associated tachinid puparia, 69 wasps were reared (13 Dec 1990, Diana Beach, 90/113A).

MJWC reared a female of a solitary species of Brachymeria (Chalcididae) from a field collected pupa at Bamburi Beach, Kenya (6 Sep 1988, 88/77B). This individual survived for a month fed on honey, but would not parasitize the pupae of Helicoverpa armigera (Hübner) (Noctuidae) which were exposed to it. A different, gregarious Brachymeria sp. (apparently the same species as reared from Z. cerymica above), was also reared from field-collected pupa from Diani Beach: eight adults emerged from one approximately 2.5mm diameter hole cut through the wing sheaths of one pupa (26 Mar 1989, 89/19C), while 15 adults emerged from three holes (two of 1.4mm and one of 2.6mm) cut in the thorax of another (23 Aug 1995, 95/107D). Similar material from coconut, Watamu, coastal Kenya (Oct 1993, SCC) is preserved in ABRI. Empty field-collected pupae with similar emergence holes of diameter about 2.5mm were found on more than one occasion at the Kenya coast, which could have been due to either of these Brachymeria spp.

Finally, from material collected on Raphia farinifera at Shiwa Ng’andu (northern Zambia), TCEC reared a large yellow and brown ichneumonid larval pupal parasitoid, similar to that reared from Ploetzia amygdalis (above); it too emerged by pushing the head off the host pupa.

Discussion. As noted in the introduction to this species, at present the scattered records from Kenya, Tanzania and Zambia suggest isolated populations. From what we know now of the palm food plants (above), it seems quite likely that further collecting will show that these populations are connected, at least along rivers. We have noted geographical variation in adult phenotype between these populations, and we document some differences between caterpillars from different areas, in particular between the Kenya coast population and those of Tanzania and Zambia. However, we have noted that there is some variation in body and head markings amongst the final instar material from the Kenya coast ( Figure 31 ), but we don’t have this information for Tanzanian and Zambian populations, so cannot assess to what extent the differences in markings may overlap when variation is taken into consideration. As yet, we have no observations from the western part of the range of C. carmen . Thus, our observations do not resolve the question of whether this is a single variable species, or whether there are distinctive geographically separated populations, which may or may not merit subspecies status. More detailed observations and documented individual rearing from several areas should help clarify things, and the use of molecular methods should also help.

Figures

FIGURE 28. Adult Gretna carmen capra collected as caterpillars on Cocos nucifera, 22 Sep 1989, Malindi, Kenya; adults 14 Oct. 1, male, 89/61E; 2, female, 89/61C.

FIGURE 29. Ornamental palm used as food plant by Gretna carmen capra and identified as a Neotropical Roystonea sp.; Diani Beach, Kenya, 22 Aug 1995; 95/109.

FIGURE 30. Young caterpillars of Gretna carmen capra collected on Cocos nucifera, Kenya. 1, newly moulted?third instar caterpillar, Bamburi Beach, Kenya; collected and photographed 6 Sep; not reared; 88/77. 2, fourth instar caterpillar, dorsolateral view, collected as second instar caterpillar, Diani Beach, 22 Aug 1995; moulted to fourth instar 29 Aug; photographed 1 Sep; died; 14mm; 95/107E.

FIGURE 31. Final instar caterpillars of Gretna carmen capra, collected on Cocos nucifera, 22 Sep 1989, Malindi, Kenya. 1, head, anterodorsolateral view; moulted to final instar and photographed 26 Sep; 24mm; 89/61H. 2–3, photographed 26 Sep; pupated 1 Oct; 40mm; 89/61F; 2, head anterodorsal view; 3, caterpillar with wax glands developed laterally, dorsolateral view.

FIGURE 32. Prepupa of Gretna carmen capra, collected on Cocos nucifera, Bamburi Beach, Kenya, 6 Sep 1988; photographed 6 Sep; pupated 8 Sep; 88/77C.

FIGURE 33. Caterpillars of Gretna carmen, Tanzania [TCEC]. 1, young instar collected on Raphia, Chivanjee, Tukuyu, southwestern Tanzania, 7 Nov 1995; 2, final instar, detail of head, anterodorsal view; collected on Elaeis sp., Kigoma Town, western Tanzania. 1 Mar 1997; 3, final instar, detail of head, anterodorsolateral view; collected on Raphia, Chivanjee, Tukuyu, 24 Feb 1994; 4, final instar, dorsal view, collected as #1; 7 Nov 1995; 5, final instar, dorsolateral view, collected on Raphia, Tukuyu, 16 Nov 1995.

FIGURE 34. Lateral view, field collected pupae of Gretna carmen capra, on Cocos nucifera, Bamburi Beach, Kenya, 7 Sep 1988; pupa on right emerged 8 Sep, that on left 15 Sep; 25mm; 88/77A.

FIGURE 35. Mummified caterpillar of Gretna carmen capra, with puparia of Palexorista sp., collected 26 Mar 1989, on Cocos nucifera, Diani Beach, Kenya; adult flies 2 Apr; 89/19A.