Eretis lugens ( Rogenhofer 1891 )

COCK, MATTHEW J. W. & CONGDON, T. COLIN E., 2011, Observations on the biology of Afrotropical Hesperiidae (Lepidoptera) principally from Kenya. Part 3. Pyrginae: Celaenorrhinini, Zootaxa 3033 (1), pp. 1-67 : 39-42

Eretis lugens ( Rogenhofer 1891) ( Figures 39–43 )

This species was described from Marangu (SE of Kilimanjaro in Tanzania) and is found from Kenya to Sierra Leone and Ethiopia to Angola. Judging by the series in the NHM it is particularly common in Kenya and Uganda.

E. lugens is widespread in upland Kenya (over 1000 m), and common along forest margins and hedges, in gardens and on rough ground with trees and scrub. In most of upland Kenya, this is the only Eretis sp. , since E. djaelaelae and E. umbra are savannah species, and the other four are restricted to the forests of western Kenya. The male of E. lugens has the fore-leg femora fringed with white. Evans (1937, p. 36) accidentally gives this character as brown (although his Plate 2.15 shows this correctly), and subsequently he corrected this ( Evans 1947).

Adult behaviour

Males and females rest on vegetation with their wings open ( Figure 39 ), and come readily to flowers. Some- is probably also true of most Pyrginae which rest with their wings flat. Flight is rapid, and difficult to follow, but individuals often return to the same perch. The ovipositing female rests with her wings held upwards at a slight angle, and the abdomen angled downwards (87/15).

Food plants

I have found caterpillars of this species at Kakamega (3 collections), Kisii (4 collections), Nairobi (5 collections) and Ngong Forest (once) on what I identified as Dyschoriste nagchana (= perrottetii) ( Acanthaceae ). However, when I photographed the food plant growing naturally in my Nairobi garden ( Figure 40.1 ) I actually photographed a plant of D. multicaulis , which has hairy stems where those of D. nagchana are smooth. Clearly I had not differentiated these two Dyschoriste spp. My herbarium specimens from Kisii and Nairobi confirm that D. nagchana is a food plant of E. lugens , but Figure 40.1 of a leaf shelter in my garden is of D. multicaulis showing that this is a natural food plant too.

Sevastopulo (unpublished) reared E. lugens from caterpillars collected on Barleria sp. (Acanthaceae) in Uganda, and includes this food plant in Sevastopulo (1975), along with Asystasia (Acanthaceae) . Van Someren (1974) records A. mysorensis (= schimperi), A. gangetica (= A. coromandeliana ) (?) and Justicia leikpiensis (J.

leikepiensis, J. lukepiensis are mis-spellings in the Lepidoptera literature) ( Acanthaceae ) as food plants. Kielland (1990), Larsen (1991, 2005) and Heath et al. (2002) repeat these records. I have offered A. mysorensis to caterpillars from D.? nagchana but they would not feed. Figure 40.2 shows an empty leaf shelter on A. mysorensis , but the absence of associated feeding and the distal slit suggests this is more likely to have been made by a gryllid, than an Eretis sp. Vuattoux (1999) reared seven examples of E. lugens from D. nagchana in Côte d’Ivoire.

Ovum

The ovum is laid in the middle of the leaf upper surface; when newly laid, it is greenish white, but over a few days it changes to pale red ( Figure 41.1 ). The ovum has about 13 white ridges rising from the base to alternately reach just short of the top or reach 2/3 of this. It measures 0.64 mm diameter and 0.45 mm high (89/15B). An ovum which I saw laid on D. nagchana at Kisii on 22 Mar 1989 hatched after six days .

Leaf shelters

Early shelters are formed from a young terminal leaf, simply folded upwards along the mid-rib and sealed at the edges. Sometimes the leaf lamina is cut near the base from the margin to the mid-rib so that the basal portion is held as normal, and the distal portion is folded over to form the shelter. There is some feeding by young caterpillars on the leaf surface inside the shelter, which must provide shelter from predators and parasitoids.

Caterpillar moulted; head black with scattered pale setae, stalked with a palmate flat distal area held parallel with the head; body dark reddish brown; legs concolorous. The mature caterpillar is as shown in Figure 42 ; when newly moulted it was 11 mm long; head black, covered in scattered white scales as penultimate instar; T1 paler immediately posterior to head; body dark black-brown (greenish in some individuals), with scattered dots of yellowish white, which under magnification can be seen to be very short, pale, stalked, stellate setae; paler below spiracles; a dorsolateral row of pale brown spots on anterior margin of T3–A7 (weak on T3–A1); white-brown spiracles quite conspicuous. Head measurements were made on preserved material wide x high (number of observations) as follows: instar 2 (n–3) 0.55 x 0.58 mm (2); instar 3 (n–2) 0.88 x 0.93 mm (6); instar 4 (n–1) 1.39 x 1.46 mm (7); instar 5 1.99 x 2.05 mm (4). The caterpillar which hatched from the ovum that I collected at Kisii immediately after it was laid took 58 days to reach pupation. Observations of instar duration include instar 3: 7 days; instar 4: 8 days (7, 7, 7, 8, 10); final instar 17 days (11, 12, 17, 18, 20, 23).

The caterpillars are very similar to those of E. umbra maculifera ( Figure 37 ), but the two butterflies occur in different habitats, so are unlikely to co-occur.

Pupa

Figure 43 shows the pupa of collection 89/40 on Dyschoriste ? nagchana , at Kakamega Forest: 13 mm; rounded outline; proboscis sheath projects 2 mm beyond wing cases; scattered erect pale hair-like setae except on appendages and line down middle of eye. Front of head between eyes, anterior part of eyes, and dorsal part of head extending to T1 spiracles black; rest of head light green. Thorax and appendages light green; spiracle T1 black, protuberant. Abdomen light brown; narrow, dark, diffuse dorsal line; spiracles light brown, those of A1–A 2 in dark patch; anal segment dark. The pupa takes 14 days (9, 11, 13, 15, 16, 19) to complete development, giving a total development time of 79 days from egg to adult under Nairobi conditions, suggesting about five generations could be completed per year.

Natural enemies

An ovum collected on Dyschoriste ? nagchana at Kisii on 22 Mar 1989, yielded a single egg parasitoid 11 days later. A leaf shelter collected at Kakamega on D.? nagchana on 17 May 1989 contained two small (1.5 mm) white eulophid pupae. These turned black and emerged on 26 May 1989. Extrapolating from other hesperiids, the eulophid larvae would have been external parasitoids of a small paralysed host caterpillar.

Caterpillars collected in Nairobi are quite commonly parasitized by a gregarious Apanteles (s.l.) sp. Parasitized caterpillars were collected in the penultimate or final instar, and the parasitoid larvae emerged from the mature final instar caterpillar. The cocoons are formed scattered within the leaf shelter. The recorded sex ratios are female biased, but not strongly: 5♂, 5♀ (89/34C), 4♂, 3♀ (90/89B), 2♂, 14♀ (90/89C), 14♂, 10♀ (91/30A), 4♂: 7♀ (91/

Figures

FIGURE 37. Final instar caterpillar of Eretis umbra maculifera. 1, collected as n–2 caterpillar on Acanthaceae (probably Dyschoriste radicans, Figure 36), Cottar’s Camp, Masai Mara, 19 Feb 1990; moulted to final instar 7 Mar; photographed 25 Mar 1990, 12 mm; pupated 3 Apr, 90/21. 2, as (1) but photographed 12 Mar 1990.

FIGURE 39. Adult of Eretis lugens. 1, male, Muguga, 10 Nov 1988. 2, female, Ngong Forest, Nairobi, 12 Sep 1989. 3, Muguga, 10 Nov 1988, showing the flexure of the wings when held ‘flat’.

FIGURE 40. Possible food plants of Eretis lugens. 1, Dyschoriste multicaulis, Nairobi, Jun 1990 (D. nagchana is similar but has smooth stems). 2, Empty shelter probably made by a gryllid, on Asystasia mysorensis (= schimperi), Gatamaiyu Forest, 5 Jul 1998, 98/204.

FIGURE 41. Ovum and leaf shelters of Eretis lugens. 1, Ovum observed being laid on Dyschoriste nagchana, 0.64 mm diameter, 22 Mar 1989, Kisii; photographed 24 Mar; hatched 28 Mar; 89/15C. 2, leaf shelter on D. multicaulis containing n–2 caterpillar, Nairobi, 27 Jan 1990, 90/15B. 3, close up of (2).

FIGURE 42. Final instar caterpillar of Eretis lugens, collected in leaf shelter similar to Figure 41.2–3 on Dyschoriste?nagchana, Nairobi, 6 May 1989, 13 mm; parasitized by Apanteles (s.l.) sp.; 89/34C. 1, dorsolateral view; 2, detail of head anterolateral view.

FIGURE 43. Pupa of Eretis lugens. 1, lateral view, collected as n–2 caterpillar on Dyschoriste?nagchana, Kakamega Forest, 16 May 1989; pupated 18 Jun; photographed 19 Jun, 13 mm; adult 2 Jul; 89/40. 2, ventrolateral view, wings forming up; collected as n–1 caterpillar on D.?nagchana, Ngong Forest, Nairobi, 17 Sep 1989; pupated 18 Oct; photographed 26 Oct; died; 89/55.