Zophopetes cerymica Hewitson 1867

Zophopetes cerymica Hewitson, 1867 (in Hewitson 1867 –1871)

Hewitson (1867 –1871) described Hesperia cerymica from Akwa Akpa (=Old Calabar, south-eastern Nigeria). Evans (1937) treated cerymica as two subspecies: the nominate cerymica in West Africa, from Senegal as far east as Cameroon, and what he referred to as nobilior Holland, the eastern subspecies, described from Gabon (Lambarene, French Congo), but for which Evans only listed specimens from Uganda, Kenya and Tanzania, although it also occurs in DR Congo (Kielland 1990, Ackery et al. 1995) and north-west Zambia (Heath et al. 2002). Lindsey & Miller (1965) treated cerymica and nobilior as full species, based on differences in the male genitalia, and this has been followed by subsequent authors, although Larsen (1991) suggested they may be subspecies, when documenting the population from the Kenya Coast as Z. nobilior.

T.B. Larsen (pers. comm. 2013) has now established that the taxon referred to as nobilior is not that species, which is currently only known from two females from Gabon, and near Mbandaka in western DR Congo that are much smaller than Z. cerymica and with a rather different hind wing underside.

Although Lindsey & Miller (1965) considered that the male genitalia of Z. cerymica from West Africa and East Africa (their Z. nobilior) represent different species, T.B. Larsen (pers. comm. 2013) notes that the material treated as nobilior by Evans falls within the range of variation in colouring and male genitalia seen in Z. cerymica, so that for the moment at least, it would be more appropriate to treat this as a single variable species without subspecies. We have seen caterpillars from Togo, Côte d’Ivoire, Kenya (coast), Tanzania and Zambia, which we illustrate separately here. There are no significant differences between the early stages of these populations, supporting the view that Z. cerymica is a somewhat variable species found from Senegal, east to Kenya and south to Zambia. However, given the variation that we have reported in caterpillars and male genitalia indicating complex species or species-complexes in the other Zophopetes spp. above, this conclusion perhaps should be considered provisional pending more detailed studies.

In Kenya this species is restricted to the coast, where coconut is a regular food plant. Although not as common as those of Gretna carmen capra Evans on coconut, caterpillars can be found without too much difficulty. In Tanzania, it is found in forests on the eastern shore of Lake Tanganyika, and in eastern Tanzania it is known from Dar es Salaam, the Pugu Hills, and the Lukosi River near Iringa (Kielland 1990). It is not confined to forest, for example, on the Lukosi River as it flows through dry thorn scrub and rocky Acacia woodland for the last 20–30 km to its junction with the Great Ruaha, it breeds on Raphia palms growing on the banks and islands among the channels of the fast flowing river bordered by very degraded remnants of riverine forest. In Zambia it is restricted to the north-west (Heath et al. 2002).

Adult behaviour. We have no observations, but Genty (1968) notes in Côte d’Ivoire that Z. cerymica adults (Figure 19) fly at dusk and are attracted to light, Sevastopulo (1964) records this species attracted to light by night in East Africa, and most of the material that T.B. Larsen (pers. comm. 2014) has of this species is from the restaurants of beach hotels in Ghana, as well as at the Cape Three Points lighthouse. Boorman (1970) writes that in Nigeria adults fly at dusk and come to papaya flowers, and Kielland (1990) notes in Tanzania that this species also flies in the early morning when it also comes to flowers. Forsyth (1966) records adults sucking citrus fruits on trees in Ghana.

Food plants. As noted above, early reports of Z. dysmephila as a palm pest in the French West African literature were misidentifications for Z. cerymica (rather than Z. quaternata, which Z. dysmephila resembles). The associated descriptions and figures of the early stages (e.g. Genty 1968, Mariau & Morin 1974) match Z. cerymica rather than Z. dysmephila, and Z. cerymica replaces Z. dysmephila in more recent publications (Mariau et al. 1981, Mariau 2000, 2001). Thus, Z. cerymica (as Z. dysmephila) is recorded from oil palm (E. guineensis) at Anguédedou, Côte d’Ivoire (Genty 1968). Mariau & Morin (1974) give a general account of Z. cerymica (as Z. dysmephila) and Pteroteinon laufella (see below) as pests of oil palm and coconut in West Africa. The pinned adult butterfly they illustrate as Z. dysmephila appears to be a female Z. cerymica, and the authors refer to the head of the caterpillar as uniformly golden yellow (uniformément jaune d'or), which is diagnostic for Z. cerymica (Figure 20–24) compared to Z. dysmephila (Figures 7–13). We note that although the paper title specifies hesperiid defoliator pests of oil palm and coconut, the text only refers to oil palm. Vuattoux (1999) only reared this species from E. guineensis in Côte d’Ivoire. In Ghana, T.B. Larsen (pers. comm. 2013) found it most frequently along beaches with many coconut palms (especially between Cape Coast and Takoradi).

Early food plant records from East Africa were under the name Z. cerymica, anticipating the present arrangement. Thus Van Someren (1974) gives Raphia spp. and Cocos nucifera (as Cocoa nucifer) as food plants of Z. cerymica in his list of food plants of East African butterflies. Sevastopulo (1975) repeats these records, and later adds Phoenix (Sevastopulo 1981).

Treating this species as Z. nobilior, Kielland (1990) lists the food plants as Phoenix, Borassus and Raphia palms, but doesn't mention coconut. Larsen (1991) adds coconut, based on MJWC’s rearing, and repeats these food plants for Z. cerymica (Larsen 2005). Ackery et al. (1995) list the food plants of Z. cerymica as Borassus, Phoenix and Raphia. Heath et al. (2002) give the food plant in north-west Zambia as Raphia sp.

In Kenya, MJWC found this species on Cocos nucifera only, whereas TCEC found caterpillars on E. guineensis in Tanzania, and on Raphia farinifera in Tanzania and north-west Zambia, although some were transferred from R. farinifera to C. nucifera in order to rear them through. Both authors have tried independently to transfer caterpillars to feed on leaves of P. reclinata, and failed. MJWC tried with one caterpillar that only fed a little and then died (89/18B). We doubt that Phoenix spp. are normal food plants of Z. cerymica. We also have reservations about the repeated records from Borassus spp., which TCEC has searched without finding any Hesperiidae early stages. MJWC has also reared Z. cerymica from C. nucifera at Lomé, Togo (90/213), and found a caterpillar on an unidentified planted palm in Côte d’Ivoire (88/214).

Leaf shelters. On R. farinifera at Lukosi River, Tanzania, TCEC noted that the young caterpillars roll the tip of a leaf into a tube and eat their way back down the leaf as they grow. When the midrib becomes too tough, the shelter is abandoned, after the caterpillars have eaten down to it from one or both sides.

The medium grown caterpillars (penultimate or previous instar) feed from the apex of a leaflet, where they make a shelter by rolling one or both edges of the leaflet over upwards. Rolling the flap upwards is the line of least resistance, as the young leaflets are naturally V-shaped, and if they rolled downwards caterpillars would have to deal with the sharp thorns on the underside of the midrib of the leaflet. Fully grown caterpillars make a tubular shelter, usually at the apex of the partly consumed leaflet, by rolling both edges of the leaflet under. Feeding usually leaves the distal end of the leaflet truncate, but pointed at the midrib.

Pupation was either in a tube as used by mature caterpillars, or in a shelter made between two leaflets, one on top of the other (7 Nov 1990, Lomé, Togo, 90/213). A pupal shelter found at Diani Beach, Kenya (26 Mar 1989; 89/18A) was made about 25cm from the apex of a C. nucifera leaflet on which there had been no feeding. The edges of the leaflet were held with thick strands of silk to make a tube, and the posterior (basal) portion had been largely blocked off with silk webbing. About 50mm of the shelter was lined with white waxy powder which was also present on the pupa.

Ovum. The ova are laid on the leaflets of C. nucifera; they are similar to those of Z. dysmephila but larger. Mariau & Morin (1974) and Mariau et al. (1981) refer to the ova of Z. cerymica and Pteroteinon laufella as 1.5mm in diameter and laid in variable numbers (en nombre variable) on the leaflet under surface. Ova from the Kenya coast measured 1.8 x 1.2mm wide x high (n=2). Ova hatch in 5–6 days (Genty 1968). We have found ova of Z. cerymica only singly, so suggest that the references to ‘variable numbers’ should be considered to apply to P. laufella only, until new observations suggest otherwise.

Caterpillar. Brief descriptions of material from the Kenya coast were prepared based on collection 87/22 (Diani Beach, 29 Sep 1987), which was not successfully reared, but considered to match later collections that were. When collected in the penultimate instar, the caterpillar measured 24mm; head light brown with diffuse central marking on face; narrow dark pronotum; body creamy green with a yellow dorsolateral stripe; anal plate speckled yellow. This brief description is compatible with Figure 20.1, where the detail of the marking on the central face can be seen, the pronotum is white on the anterior margin, and the spiracles are inconspicuous. Four head capsules measured 3.0 x 3.5mm wide x high (range 2.9–3.1, 3.3–3.7).

The mature caterpillar (Figure 20) is one of the largest of Kenyan skipper caterpillars, measuring up to 46mm and taking about 14 days to complete development. The head capsule measures 4.0 x 5.2mm wide x high (range 3.8–4.3, 4.6–5.6, n=6). Caterpillar 87/22 moulted to the final instar three days after collection, and on the following day (4 Oct) it measured 28mm (Figure 20.4). Head 3.9 x 4.8mm wide x high; shiny, rugose; plain yellow brown except for a black posterolateral band from just before vertex, where it is narrow with a brown posterior margin, widening to the bottom where it runs from the posterior margin to the stemmata. Shiny black pronotum to just above spiracles. Body pale green; T2–A9 a dorsolateral yellow-white line, about 1mm wide; spiracles light brown; anal plate almost chordate; flanged posteriorly; a network of yellow markings anteriorly. Subsequent collections have shown that the black lateral marking of the head may be reduced to a basal bar from near the posterior margin to the stemmata (Figure 21.3) or just a small black spot covering the stemmata (Figure 20.2). When it has finished feeding, the caterpillar turns dirty yellow, losing the dorsolateral lines (Figure 20.6)

The final instar caterpillar recorded in Tanzania is similar (Figure 21). The head marking of the caterpillar shown (Figure 21.3) is an extensive black marking from the vertex laterally, and anteriorly to the stemmata, as heavy as the heaviest documented from Kenya (Figure 20.4). Instar 2 (Figure 21.1–2) has the dorsal two-thirds of the head dark, almost black, and the ventral one-third brown; body pale green with pale subdorsal lines.

The caterpillars from Zambia are also similar. The early instars were not reported from Kenya (above), but instar 1 from Zambia (Figure 22.1) can be seen to have a brown head, with a dark brown line adjacent to and close to the epicranial suture; darker on the frons; narrow black pronotum and a plain yellow-green body. In the penultimate instar (Figure 22.2–3) the yellow-brown head has a W-shaped mark on the face, the outer arms parallel to the epicranial suture, and a diffuse dark patch over the dorsal part of adfrontals and adjacent epicranium. The final instar shown in Figure 22.4–6 appears to be mature and starting to turn yellow. It is similar to that from Kenya; in the example photographed there is a minimal black marking around stemmata (Figure 22.4), comparable to one example from Kenya (Figure 20.2).

No detailed description of the caterpillar was prepared for the caterpillars from West Africa, but they were documented with photographs (Figures 23–25). The n-2 instar head (Togo 90/213) measures 2.1 x 2.6mm wide x high (n=3); pale brown; bottom of epicranial suture and clypeal sutures dark; short diffuse, dark line parallel to epicranial suture from just above top of adfrontals to level with top of frons; posterior margin dark. The penultimate instar measures 3.1 x 3.7mm wide x high (n=4); face of the penultimate instar from Togo (Figure 23) has a variable diffuse W-shaped mark across the top of the adfrontals and adjacent epicranium; stemmata black, sometimes with a black patch around them; posterior margin dark in some individuals. This instar is intermediate to that shown from Kenya (Figure 20.1) and that shown from Zambia (Figure 22.3).

In the final instar from Togo (Figure 24), the head is 4.2 x 5.1mm wide x high (n= 3, 6); plain orange brown, apart from a black patch around the stemmata (Figure 24.2), matching Figure 20.2 from Kenya; T1 broadly white, with a narrow black pronotum; body white, more or less opaque, with broad yellow dorsolateral stripes with diffuse edges; T1–3 and A9 and anal plate with a strong yellow tint; spiracles pale brown, contrasting with white body; legs concolorous. The caterpillar takes about a month to develop (Genty 1968).

The body of the caterpillar from Côte d’Ivoire (Figure 25) is a brighter white than those from Togo (Figure 24), but otherwise there is no great difference. It too has a small black spot over the stemmata like Figure 20.2 from Kenya.

Pupa. Pupae were not described, but are similar in all populations; the interior of the pupal shelter and the pupa are both covered with white waxy powder (Figure 26). They are superficially similar to those of Z. dysmephila, but larger (25–34mm), and the proboscis sheath extends 7mm beyond the wing cases (Figure 26.4). The pupa is held by a girdle consisting of 10–14 strands of thick silk; erect setae dorsally on the thorax and forward directed setae dorsally on the posterior part of A1 (which grip the silk girdle); erect setae dorsally on A2–A4; a protuberance frontally, a pair of protuberances just above this and one at the base of the antenna. One character noted on West African and Zambian material is a tuft of backwardly angled stiff brown setae dorsolaterally on a thickened area at the base of the cremaster. Kenyan material is similarly thickened but lack the tuft of setae (Figure 27). We do not know the function or significance of this character. However, there are rare observations of more robust structures in this situation in other species of Hesperiinae, which suggest a possible function. Cock (2010b) noted a robust dorsal plate on the dorsal posterior end of the pupa of the Neotropical Anthoptini species Corticea corticea (Plötz), with two robust posterolateral spikes on each side and suggested that since pupation is in a tightly rolled grass leaf shelter, this posterior plate may be used to prevent access by parasitoids or small predators which may enter the pupal shelter at the posterior end; the heavily chitinized plate would be difficult for small predators to attack, and the posterolateral spikes at the side could be used to crush an intruder against the side of the shelter. The pupa of the Asian palm-feeder Gangara thyrsis (Fabricius) (Hesperiinae, incertae sedis) has a very strong posteriorly directed spike at this point (Figure 28.2) which may also have a defensive function. The pupal stage lasts 21–23 days under Nairobi conditions, although in Côte d’Ivoire, Genty (1968) recorded the duration as about a month.

Natural enemies. Mariau & Morin (1974) did not distinguish between Pteroteinon laufella and Z. cerymica, when they treated the natural enemies of these two skippers in West Africa. However, more recently, Mariau (2001) treats all the same natural enemies under P. laufella and mentions none for Z. cerymica, so we follow this arrangement here. The only exception to this is the record of an unnamed entomopathogenic fungus, which is illustrated on a pupa of Z. cerymica (Mariau & Morin 1974, Figure 9). The single caterpillar which MJWC found at Adiopodoumé, Côte d’Ivoire, had several macrotype tachinid ova on its body (Figure 25), but it died at pupation.

MJWC reared several parasitoids from material collected on C. nucifera at the Kenya coast. Ova are parasitized; two adults of an unidentified orange species emerged from an ovum collected at Diani Beach (29.iii.1989; 89/23). The corpse of a fourth instar caterpillar was found in its shelter surrounded by empty euplectrine pupae (Diani Beach, 22.viii.1995; 98/110), but living material of this parasitoid has not been obtained. A field-collected pupa from Diani Beach (26.iii.1989; 89/18A; Figure 26.4) was parasitized by a gregarious Brachymeria sp. (Chalcididae), which appears to be the same species reared from Gretna carmen capra (below); 37 adult wasps emerged from the one pupa, 20 days after collection. A three-quarter circle of diameter 2.2mm was cut in the sub-dorsal abdomen, through which the adult wasps emerged. Although there was some white waxy powder on the inside of the pupal shelter, there was very little on the parasitized pupa itself (Figure 26.4). An empty field-collected pupa collected on the same occasion (89/18C) had a 3.0mm diameter emergence hole probably made by a Brachymeria sp.

Economic damage. Mariau & Morin (1974) state that Z. cerymica (as Z. dysmephila) is commoner on oil palm than Pteroteinon laufella, but do not separate the two species in their assessment of the damage. Genty (1968) describes an outbreak in Côte d’Ivoire where up to three-quarters of the foliage was eaten. Outbreaks can occur on oil palms of all ages, including newly planted estates. Defoliation at this stage can be severe (Genty 1968) and set back crop development. Attacks on older palms are less common, the damage usually less serious and normally localised on the edge of plantations. An economic threshold of 20 hesperiid caterpillars per frond has been proposed for mature palms, based on a sample of two fronds per ha at the point of heaviest attack (Mariau et al. 1981).

There have been no reports of Z. cerymica occurring in high enough numbers to cause damage to palms in East Africa, or elsewhere in its range, perhaps because of the action of natural enemies keeping populations in check. Nevertheless, Z. cerymica should be considered a quarantine pest for areas outside Africa where palms, especially coconut and oil palm are grown.

Discussion. The caterpillars and pupae of Z. cerymica appear almost identical throughout its range. The variation in the extent of the black ventrolateral marking seen on the head of the final instar caterpillar from different collections in Kenya encompasses all forms seen elsewhere. The presence of the tuft of setae dorsolaterally at the base of the cremaster of West African pupae but not on those from East Africa is the only consistent difference we have noticed between the two areas. Nevertheless, at this stage, treating Z. cerymica as a single slightly variable species throughout its range seems reasonable.