Platylesches moritili Wallengren, 1857

Cock, Matthew J. W. & Congdon, Colin E., 2013, Observations on the Biology of Afrotropical Hesperiidae (Lepidoptera). Part 5. Hesperiinae incertae sedis: Dicotyledon Feeders, Zootaxa 3724 (1), pp. 1-85 : 63-70

Platylesches moritili Wallengren, 1857

Described from ‘Caffraria’ (southern Africa) ( Wallengren 1857), this species in widespread through West Africa, east to Kenya, and south to northern South Africa ( Evans 1937, Larsen 1991). Larsen (1991) records it from the Kavirondo area of Kenya, but not elsewhere in that country. However, ABRI collectors have since found it breeding on Pa. curatellifolia near Embu in dry bush.

Congdon et al. (2008) report rearing a variety of caterpillars, with different head markings, the adults of which all appeared to be Pl. moritili . The information presented here is based on the work described in Congdon et al. (2008), with updates where available, but there has been no subsequent progress sorting out the taxonomy of this species or species complex. In the following we designate the different caterpillars as forms, i.e. deliberately choosing a level with no taxonomic validity. At this time we recognise that the different caterpillar heads probably represent different species, but they may also represent different haplotypes of a single polymorphic species. We note that Larsen (2005) illustrates two different male genitalia, both apparently belonging to ‘ Pl. moritili ’, but actually representing Pl. moritili and the new species referred to above (T.B. Larsen, pers. comm. 2012). Clearly, more work is needed.

Larsen (1991) remarks that this may be a species of the transition zone between forest and grassland in Kenya. It also occupies this habitat on the Rondo, but in South Africa, Zimbabwe, Zambia and at Mufindi, Tanzania, it is a butterfly of woodland and wooded savannah grassland. If more than one species is involved, this variety of habitat preference is not surprising.

Adult behaviour

In the National Botanic Gardens , Harare, MJWC observed that males perched on tall grasses (c. 2m) under an open canopy, and returned to their perches after swift territorial flights.

Food plants

Early last century, Dollman (unpublished) reared Pl. moritili from ‘mupundu’ (i.e. the wemba name for mbolola or mbola plum, Pa. curatellifolia ) in central Zambia (Mwengwa) and north-western Zambia (Solwezi), and painted the caterpillar. Woodhall (1994) documented rearing Pl. moritili from caterpillars collected on Pa. curatellifolia in Limpopo Province, South Africa, in 1989, and this food plant record is repeated by subsequent authors ( Pringle et al. 1994, Heath et al. 2002, Henning et al. 1997, Woodhall 2005, Larsen 2005). The food plant in Ghana may be Maranthes polyandra (= Pa. polyandra ) as suggested by Larsen (2005). MJWC found caterpillars on Pa. curatellifolia near Harare, Zimbabwe and TCEC has reared this species from Pa. curatellifolia in Tanzania, Malawi, Zambia and Zimbabwe.

Leaf shelters

Based on observations on form beta at Mukuvisi Woodland, Harare (MJWC 88/24), small leaf shelters are made on flush leaves by cutting a semi-circular flap from the edge of the lamina. The shelters of medium grown to near full grown caterpillars are made by rolling an edge of the leaf under to reach the mid rib, and holding it with 8–10 thick, multiple strands of pinkish silk, to make a tube 30–45mm long. TCEC found that shelters do not usually involve cuts and may involve one or both edges of a leaf being rolled under ( Figure 70 ). We have not carefully evaluated whether the different caterpillar forms show consistent differences in their shelter construction, but there are no obvious patterns.

Ovum

An ovum photographed by TCEC ( Figure 71 ) is similar to that thought to be of Pl. galesa ( Figure 66 ), salmon pink with about 16 wall-like ribs.

Caterpillar

The commonest form on on the Rondo Plateau, south-eastern Tanzania, but also found at Mufindi, Udzungwa Mountains, Tanzania, and once near Harare, Zimbabwe, was form alpha ( Figure 72.1–2 ). Form beta ( Figure 72.3– 5 ) also occurred on the Rondo Plateau, as well eastern Zambia, and north-western Zimbabwe, but was dominant at Mufindi. Other patterns of head markings were found in eastern Zambia and western Zimbabwe ( form gamma Figure 72.6–7 , and form delta Figure 72.8–10 ). The adults of all forms appear to be moritili . In the majority of cases TCEC’s team were dealing with good series of each form from each locality. In localities where there was more than one form, they did not find intermediates between the various head patterns. Where there was only one form, as at Hwange in Zimbabwe, it was constant in appearance. Fully fed caterpillars of all these types turned red prior to pupation ( Figures 72.10 and 75.1 ).

Platylesches moritili form alpha caterpillar

This form has the darkest head capsule, being black with an arc of white spots on the epicranium, a pair of very pale yellow-brown spots on the adfrontals, and a white spot on the frons ( Figure 72.1–2 ). This form was found abundant on the Rondo Plateau at about 850m, south-eastern Tanzania ( Figure 72.1 ), uncommon at Mufindi, Tanzania, and once near Harare, Zimbabwe, at around 1500m in Brachystegia woodland ( Figure 72.2 ). The Rondo records are based on many collections as it was common there, but the Harare collection on a single caterpillar, which died soon after collection.

The final instar of form alpha appears to be similar to penultimate instars of form gamma (below). The caterpillar which Henning et al. (1997) illustrate as an early instar (alongside a final instar of form delta ) is a good match. However, the caterpillar in the photo seems to have a newly cast skin at the anal end and the size of this caterpillar in proportion to the food plant leaf suggests that it is at least in the fourth instar, probably fifth, in which case it could be a final instar of form alpha .

Platylesches moritili form beta caterpillar

In this form, the face is black with larger white spots on the epicranium than form alpha , larger and browner spots on the adfrontals (but not extending to the dorsal end), and laterally a broad brown line from the vertex to the mouthparts. It has been found below the Mufindi Escarpment, Tanzania, in savannah grassland at about 1250m ( Figure 72.3 ), where it was the dominant form, uncommonly at the Rondo Plateau, Tanzania, at Mutinondo, in eastern Zambia, in Miombo woodland at about 1500m ( Figure 72.4 ) and Hwange in north-western Zimbabwe ( Figure 72.5 ).

Platylesches moritili form gamma caterpillar

The white spots on the epicranium are slightly larger than in form beta , so that the face appears white with dark brown rays; the adfrontals are completely yellow-brown, orange brown ventrally; the frons is white, orange brown dorsally; the lateral band from vertex to mouthparts is paler ( Figure 72.6–7 ). These caterpillars have been found on Rondo Plateau, Tanzania ( Figure 72.6 ), Mutinondo, Zambia ( Figure 72.7 ), and Quiterajo, Mozambique ( Figure 73 ).

MJWC collected caterpillars which appear to be form gamma at Mukuvisi Woodland at the edge of Harare. Unfortunately none was reared through to adult, either dying or being parasitized ( Figure 74 ). The following description is based on this collection.

Stage 1 leaf shelter a semi-circular two-cut flap from edge of leaf. Stage 2 shelter a tube of 30–45mm made by folding a long flap from leaf edge upwards to centre of leaf, held by 8–10 thick ropes of multiple strands of pinkish silk. A stage 3 pupal shelter made in captivity involved folding over a flap along the length of the leaf, upwards to the centre, with the basal end left open.

A final instar caterpillar (88/24(3)) measured 20mm when collected, but had probably already shrunk as it was ready to pupate; head 3.3 x 3.5mm wide x high; round with flat face; ground colour beige, with black lines around six large white marks around edge of face, outside adfrontals, along clypeal sutures, broadly around posterior margin; adfrontals and clypeus pale. T1 concolorous. Body light whitish green, similar to the colour of the leaf abaxial surface; slightly darker dorsal line; soon after collection the body turned red, dorsal line slightly darker, spiracles white, legs reddish, body white ventrally due to wax glands but exact position not recorded. This caterpillar died as a pupa.

A penultimate instar caterpillar collected on the same occasion (88/24(2)) also measured 20mm and was similar to form beta ; head almost round with flat face; black with six round white spots around edge of face; oblique white mark at top of each adfrontal, above pale clypeus; a beige band from vertex over apex laterally to stemmata; T1 and body as final instar above; legs concolorous. This caterpillar moulted to what appeared to be the final instar although smaller than the one above (head 2.9 x 3.0mm), and was preserved in ethanol when it was killed by the emergence of larvae of an Apanteles (s.l.) sp, ( Figure 74 ).

An n-2 instar caterpillar measured 11mm; head approximately 2 x 2mm; almost round with a flat face; black, with six white spots in a ring around the face, another on clypeus. Body as the two instars above. This caterpillar moulted to a penultimate instar caterpillar similar to that described above, with a head measuring 2.4 x 2.6mm wide x high. It died in this instar and was preserved in ethanol.

Platylesches moritili form delta caterpillar

In this form the dark colouring of the face is replaced with a medium brown; the white spots are slightly more extensive than those of form gamma , so that the gaps between them are now slightly diffuse brown lines; the adfrontals are entirely pale yellow-brown, with the adjacent sutures brown; the frons is completely white; the lateral band from vertex to mouthparts is pale brown ( Figures 72.8–10 ). This is the form that Dollman (unpublished) found and painted in Zambia early last century. TCEC has found this form at Mufindi, Tanzania, in highland Brachystegia woodland at 1830m ( Figure 72.8 ), and at Mutinondo, Zambia ( Figure 72.9 ). This is also the form illustrated by Woodhall (1994) and Henning et al. (1997) as the final instar caterpillar of Pl. moritili , and probably the same as the fully mature, red caterpillar described and illustrated by Coetzer (2006), misidentified as Pl. robustus (A. Coetzer pers. comm. 2010).

Pupa

It is possible that careful documentation of the pupae will also support the division of caterpillars into forms. However, before making progress with this, it will be necessary to document and understand the colour changes that occur as the pupa develops and matures. Pupae associated with the four forms of caterpillar are shown in Figure 76 . The Pl. moritili pupa illustrated by Henning et al. (1997) associated with a form delta caterpillar is similar to those shown for forms alpha, gamma and delta. The pupa shown for form beta ( Figure 76.2 ) has the head and dorsal parts of the thorax and abdomen brown, but it is not clear that this difference is significant, rather than the result of being photographed at a later stage in development.

The pupa of form gamma (88/24) from Zimbabwe is shown in Figure 77 . It was formed within a leaf roll, in a thin but tough silk cocoon. In shape, rounded, with no protuberances, except the T1 spiracle slightly protuberant; the proboscis sheath extends 2.2mm beyond the arcuate tip of the fore wings. The cuticle was translucent, so the colouring will vary during development, recently formed, this pupa was dull white, the abdomen yellowish; frontally, a dull black arc, the arms angled ventrally; diffuse brown stripe down eye; spiracle T1 brown; thorax and abdomen with scattered pale setae, those on head and T1 shorter, erect; those on T2–3 longer curved anteriorly; those on abdomen shorter, erect, straight, angled posteriorly.

Natural enemies

A mature caterpillar of form gamma collected at Mukuvisi Woodland, Harare (88/24(2)) was parasitised by a gregarious Apanteles (s.l.) sp. ( Figure 74 ). The larvae of this parasitoid spun their cocoons in an elongate white mass adjacent to the host cadavar, with the cocoons orientating along the length of the mass. Ten female and seven male adults were obtained, and have been deposited in the BMNH.

Discussion

It appears that moritili may be a complex of several species with very similar adults, but with differing caterpillars, and perhaps differing pupae and habitat preferences. The alternative explanation is that Pl. moritili is a single species, but has a variety of distinct caterpillar forms and occurs in diverse habitats. We believe this is unlikely, given that the larvae remain hidden in their shelters during the hours of daylight, so that there would be little selective advantage in having a variety of forms. Another possibility might be that different populations have extra instars in response to environmental conditions and become progressively paler in their head markings (moving from alpha to delta), without becoming much larger. More rearing and detailed observations on the consecutive instars would be needed to assess this, but we are inclined to discount this possibility, particularly for those species that make tube shelters, which complete their development rapidly to take advantage of flush leaf growth. T.B. Larsen (pers. comm. 2012) has not noted any significant differences in genitalia of this ‘species’ from all over Africa, but has not yet purposively compared the various forms from localities where they are sympatric. Documented individual rearing of series from a variety of localities and habitats, complemented with the use of molecular methods, should resolve this interesting case.

Figures

FIGURE 66. Ova of Platylesches spp. 1, eclosed ova laid on terminal foliage of a shoot of Parinari curatellifolia, Harare, Zimbabwe, 27 Jun 1991 (91/200—a final instar caterpillar of Pl. galesa was found at the same time, but adults of Pl. moritili were also flying and the ova could have been of either species); 2, ovum of Pl. sp. on Pa. curatellifolia, Mgololo, Mufindi, Tanzania, 2 Feb 1998, TCEC (Pl. galesa and other spp. were present).

FIGURE 70. Typical tube shelters of Platylesches moritili on Parinari curatellifolia, 1 Feb 2008, Mufindi, Tanzania, TCEC. Note that the shelter on the larger leaf is made by rolling one edge under, whereas the shelter on the smaller leaf with distal feeding is made by curling both edges under to make the two halves of the tube.

FIGURE 71. Ovum of Platylesches moritili, laid on Parinari curatellifolia, 2 Feb 1998, Mufindi, Tanzania, TCEC.

FIGURE 72. Frontal view of final instar caterpillar heads of different forms of Platylesches moritili, TCEC; 1–2, form alpha; 3–5, form beta; 6–7, form gamma; 8–10, form delta. 1, Rondo Plateau, southern coastal Tanzania, in forest clearings at about 850m, 28 Feb 2007; 2, near Harare, Zimbabwe, around 1500m in Brachystegia woodland, 30 Dec 2007; 3, Mufindi Escarpment, south central Tanzania, in savannah grassland at about 1250m, 4 May 2007; 4, Mutinondo, eastern Zambia, in Brachystegia woodland at about 1500m, 23 Dec 2007; 5, Hwange, Zimbabwe, 26 Dec 2007; 6, Rondo Plateau, Tanzania, 28 Feb 2007; 7, Mutinondo, Zambia, 8 dec 2007; 8, Mufindi, Tanzania, highland Brachystegia woodland at 1830m, 26 Nov 2007; 9, Mufindi, Tanzania, 8 Dec 2007; 10, Hwange, Zimbabwe, 27 Dec 2007.

FIGURE 73. Final instar caterpillar of Platylesches moritili form gamma, collected on Parinari curatellifolia, Quiterajo, northern coastal Mozambique (1.45S x 40.26E), 2 Dec 2009, TCEC. 1, in unopened shelter, anterior view; 2, in opened shelter, dorsoanterior view.

FIGURE 74. Final instar caterpillar of Platylesches moritili form beta collected 20 Mar 1988 on Parinari curatellifolia, Mukuvisi Woodland, Harare, Zimbabwe, MJWC 88/24(2). 1, caterpillar, dorsal view, and associated cocoon mass of indet. Apanteles (s.l.) sp.; 2, detail of head in dorsoanterior view.

FIGURE 75. Final instar caterpillar of Platylesches moritili form delta, collected on Parinari curatellifolia, TCEC. 1, fully mature caterpillar ready to pupate showing typical red colour of this stage, 20 Apr 2007, Mufindi, Tanzania; 2, detail of head, anterolateral view, 8 Dec 2007, Mutinondo Wilderness, Mpika, Zambia.

FIGURE 76. Final instar head capsules and corresponding pupae of Platylesches moritili, collected on Parinari curatellifolia [TCEC]. 1, form alpha, Rondo Plateau, southern coastal Tanzania, in forest clearings at about 850m, 28 Feb 2007; 2, form beta, Mufindi Escarpment, south central Tanzania, in savannah grassland at about 1250m, 4 May 2007; 3, form gamma, Rondo Plateau, Tanzania, 28 Feb 2007; 4, form delta, Mutinondo Wilderness, Mpika, Zambia, 23 Dec 2007.

FIGURE 77. Pupa of Platylesches moritili reared from a form gamma caterpillar collected 20 Mar 1988 on Parinari curatellifolia, Mukuvisi Woodland, Harare, Zimbabwe; 19mm; died; MJWC 88/24(1).