Celaenorrhinus galenus opalinus Butler 1900

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 : 23-28

Celaenorrhinus galenus opalinus Butler 1900 ( Figures 20–26 )

There is some sexual dimorphism. The male ground colour, particularly on the fore wing upper side, tends to be more orange. The hind wing markings of the female are reduced; the spot in space 6 is separate from the large spot in spaces 4–5, while in the male it is usually joined; the markings in space 3 are often reduced to two small spots in the female, while in the male they extend over most of the space and fuse with the large spot in spaces 4–5.

The Kenya range of C. galenus opalinus extends from Meru to Nairobi and westwards to Kisii and Kakamega (where I regard it as one of the 'regular' species in Kakamega Forest ), and it is often quite common. I would expect it to turn up in any of the forests in this area, up to 3000 m. Specimens from higher altitudes (e.g. Muguga, 2135 m) may tend to be smaller .

Adult behaviour

Adults behave similarly to those of C. proxima . They come readily to flowers, will sun themselves resting on leaf surfaces in sunlight, and normally rest under leaves. The resting and feeding position is almost always with the wings held open flat ( Figure 20 ) although occasionally they will rest briefly with them only slightly open ( Figure 20.2 ).

Food plants

Around Nairobi, the food plant I have consistently found is Hypoestes aristata ( Figure 21.1 ), which is a com- found is Justicia flava ( Figure 21.2 ), which again is a common ground cover in and on the edge of wooded areas. In Kadera God Forest, near Kisii, I also found a population breeding on what was identified as H. verticillaris , which is now treated as a synonym of H. forskaolii ( Figure 28 ). Other similar Acanthaceae might well be used too. Ovum

Ova ( Figure 22.1 ) are laid on the leaf under surface in the middle of the lamina. The egg is almost hemispherical, measuring on average 0.81 mm diameter at the base (range 0.76–0.86, n=15), and height 0.6 mm (n=2). The egg shell is translucent, with on average 24.9 fine ribs (range 23–27, n=14) from the base to fade out short of the micropyle, by a little less than the width of the micropyle (0.02 mm).

Leaf shelters

The stage 1 leaf shelter is nearly always an oval one-cut shelter, 5–6 x 4–4.5 mm, in the leaf lamina, close to the empty ovum, and folded upwards and over to make a pocket, usually lying over the leaf midrib ( Figures 22.2 and 23 ). Occasionally the stage 1 shelter may be a triangular one-cut shelter from the edge of the leaf lamina. The second shelter is either oval, similar to the first but larger, or triangular (e.g. 16 x 9 mm), or semi-circular and cut from the edge of the leaf lamina ( Figures 22.3 and 23.2–3 ). The final leaf shelter is either a large flap folded under from the edge of a leaf, or formed between two leaves, one on top of the other.

Caterpillar

The caterpillars, even those in the first shelter perforate the lamina and eat out holes. Larger caterpillars feed from the edge of the leaf lamina ( Figure 22.3 ). There are five instars, and although there is a significant range of head capsule sizes in each instar, there is no overlap between instars. The following notes are based on collection 87/3 made from H. aristata in Muguga Forest, 18 Jul 1987, collection 87/7 made from the same food plant in Karen, Nairobi, 12 Aug 1987, and collection 88/14 made from J. flava in Kakamega Forest, 26 Feb 1988, supplemented by microscopic examination of preserved caterpillar remains from several collections (the setae of the head and body are at the limits of what can be characterised with a x40 binocular microscope).

Instar 1. Head dark brown almost black; smooth and shiny; several very small simple pale setae; 0.50 x 0.51 mm wide x high (ranges 0.48–0.52, 0.48–0.55, 4 measured); dull green body.

Instar 2. 4–4.5 mm. Head chordate; brown; rugose with irregular reticulate weak ridges; scattered inconspicuous short pale or translucent setae, stalked, stellate or palmate; 0.75 x 0.77 mm wide x high (ranges 0.67–0.81,

Instar 3. 7.5–8 mm. Head chordate; brown to dark brown; rugose with irregular reticulate ridges, smoother on anterior side of apex, making this area appear paler; scattered inconspicuous short pale or translucent setae, stalked and either bifurcate or stellate; 1.14 x 1.15 mm wide x high (ranges 0.98–1.24, 1.02–1.26, 9 measured). T1 dorsal plate light brown, inconspicuous. Body dull dark green, covered with scattered white dots; dorsal line clear dark green; pale dorsolateral line T2–A8; spot below dorsolateral line on A8 and anal plate with orange tint; legs concolorous; translucent whitish ventrolateral ridge, above legs.

Instar 4. 12 mm. Head chordate; dark brown; rugose with irregular reticulate ridges, smoother on anterior side of apex, and in a variable streak down face, making this area appear paler; 1.82 x 1.84 mm wide x high (ranges 1.48–2.05, 1.45–2.14, 12 measured). T1 dorsal plate transparent. Body translucent dull dark green, covered with scattered white dots; dorsal line transparent, no dots, edges defined by edges of underlying fat bodies; narrow white dorsolateral line; ventrolateral ridge pale; brown spiracle on A8.

Instar 5. 20 mm. As instar 4 ( Figure 24 ); may have diffuse orange-red marking below dorsolateral line on A8; edges of anal plate may have red suffusion; the body appears smooth, but has very short pale or translucent setae, stellate on petiole; the same setae are denser on the anal plate which also has some longer simple pale setae. Head chordate; brown to dark brown; rugose with irregular reticulate ridges, which may be darker than the ground colour; ridges smoother and paler on anterior side of apex, and in a variable streak down face, making this area appear paler; scattered simple short straight pale setae on face; setae of lateral areas bent near apex and may be bifurcate or stellate; 2.63 x 2.69 mm wide x high (ranges 2.38–2.83, 2.50–2.96, 18 measured). I note that the irregular reticulate ridges of the final instar head capsule seem to be narrower in populations from the east of the Rift Valley (Muguga and around Nairobi) than those of populations from west of the Rift Valley (around Kakamega, Kisii).

Pupa

I have not found pupae in the wild, but in captivity the pupa is formed in a folded leaf or between two leaves, supported by an inverted Y-shaped silk girdle. Parasitized mature caterpillars are commonly found in similar shelters in the field, so it seems reasonable to interpret these as the pupal shelters. The pupa ( Figure 25 ) is notable for the extremely long proboscis sheath, and the small projection on the front of the head. It is 18 mm long; shiny, translucent light green, with the main trachea visible through the cuticle; spiracles brown; the proboscis sheath extends 13 mm beyond the wing cases and 5 mm beyond the cremaster (87/3); frontally a very short, broad, slightly bifurcate, concolorous projection; cremaster flattened and broader at the apex. Under Nairobi conditions the pupal stage lasted 13.0 days (average of 10 observations, range 9–15).

Natural enemies

The caterpillars tend to be heavily parasitized by gregarious Apanteles sp. 1 , which I have reared from Shimba Hills, Kibwezi Forest , Nairobi , Muguga , Kakamega Forest and Kisii – everywhere that I have found caterpillars of C. galenus . The female parasitoid stings the very small caterpillar. The parasitoid larvae then develop inside the host body, reaching maturity at the same time that the host caterpillar is full sized. At this stage the parasitoid larvae can be seen moving around in the host body, through the transparent cuticle. The parasitoid larvae emerge from the host caterpillar and spin their cocoons in a loose mass on either side or beneath the dying host caterpillar ( Figure 26 ). Adults take 8–9 days to emerge. The sex ratio of the resultant adult wasps is usually strongly female biased (0 ♂, 23♀; 1♂, 31♀; 2♂, 12♀; 2♂, 6♀; 3♂, 14♀; 4♂, 25♀; 4♂, 34♀; 5♂, 28♀; 5♂, 15♀; 5♂, 0 ♀; 7♂, 34♀; 8♂, 12♀; 20♂, 1♀) .

I once collected a corpse of C. galenus opalinus (Muguga Forest, 19 Jul 1988) with an associated mass of Apanteles sp. 1 cocoons. The corpse of the host caterpillar also supported several small fly larvae feeding on the decomposing tissue. In due course the wasps emerged from their cocoons, and some days later nine phorid flies also emerged. Had I collected this material from the field after the wasps had emerged, I would have only reared out the flies, and might have been misled into thinking the flies were parasitic when in fact they are saprophytic (feeding on decaying material). It is this sort of situation which has doubtless given rise to some of the erroneous records of phorid flies as parasitoids in the past.

In addition, there is a rather less common larval-pupal tachinid parasitoid, Thecocarcelia sp. , which I have reared from Kitovu Forest, Kibwezi Forest and Saiwa Swamp ( Table 1).

All three caterpillars were collected in the penultimate instar and after pupation the pupa changed from green to light brown and the tachinid maggot could be seen within; the maggot emerged from the pupa soon afterwards and formed a puparium from which the adult fly emerged. The records from Kitovu Forest and Saiwa Swamp are my only ones for caterpillars of C. galenus from these localities, yet I am reasonably confident of my identification; the host was definitely a Celaenorrhinus sp. , and almost certainly C. galenus . Sevastopulo (unpublished) notes that one pupa of C. galenus biseriata reared from a caterpillar collected at Kwale was parasitized; although he gives no indication of the classification of the parasitoid, it could have been this tachinid. Dr N.P. Wyatt of the NHM has examined my two specimens and concludes that they represent an undescribed species. There is another smaller Thecocarcelia sp. in Kenya which parasitizes Spialia spp. and is more commonly reared.

Figures

FIGURE 20. Adults of Celaenorrhinus galenus opalinus. 1, male, Ngong Forest, Nairobi, 17 Sep 1989. 2, male UNS, Ngong Forest, Nairobi, 8 Oct 1989. 3, female, collected as n–3 caterpillar on Hypoestes aristata, 29 Oct 1989, Karen, Nairobi; pupated c. 16 Dec; emerged and photographed 30 Dec 1989, 89/82B. 4, female, Kakamega Forest, 31 Aug 1995.

FIGURE 21. Food plants of Celaenorrhinus galenus opalinus. 1, Hypoestes aristata, Nairobi (transplanted), 5 Feb 1989. 2, Justicia flava, Nairobi (transplanted), 12 Mar 1989.

FIGURE 22. Ovum and early shelters of Celaenorrhinus galenus opalinus. 1, ovum collected on Justicia flava, Kadera God Forest, Kisii, 5 Aug 1990; photographed 10 Aug; solitary parasitoid emerged 14–18 Aug; 90/85B1. 2, stage 1 shelter on Hypoestes aristata, containing instar n–3 caterpillar, Ngong Forest, Nairobi, 17 Sep 1989; reared; 89/56. 3, stage 2 shelter on H. aristata, containing n–1 caterpillar, Karen, Nairobi, 29 Oct 1989; reared; 89/82A.

FIGURE 23. Diagram of stage 1 and stage 2 leaf shelters of Celaenorrhinus galenus opalinus on Hypoestes aristata, Karen, Nairobi, 12 Aug 1987, 87/7; approximately life size. Light grey is the under surface of the leaf turned over to form the shelter; mid grey is the leaf upper surface. 1, stage 1 one-cut shelter that contained an instar 2 caterpillar. 2, stage 1 one-cut shelter (empty) and stage 2 one-cut shelter that contained an instar 3 caterpillar. 3, stage 1 one-cut shelter (empty) and stage 2 two-cut shelter that contained an instar 3 caterpillar.

FIGURE 24. Final instar caterpillar of Celaenorrhinus galenus opalinus. 1, dorsolateral view; collected on Hypoestes aristata, Muguga, 26 Oct 1987; photographed 19 Nov in final instar; parasitized by Apanteles (s.l.). sp. 1; 87/31. 2, detail of head; collected on Justicia flava, Kakamega Forest, 1 Jul 1990; moulted to final instar 29 Jul; photographed 10 Aug 1990, 24 mm; 90/68.

FIGURE 25. Pupa of Celaenorrhinus galenus opalinus. 1, dorsolateral view; collected as n–3 caterpillar on Hypoestes aristata, Ngong Forest, Nairobi, 17 Sep 1989; pupated 2 Nov; photographed 3 Nov; male emerged 17 Nov; 89/56. 2, lateral view, collected as n–1 caterpillar on H. aristata, Karen, Nairobi, 29 Oct 1989; pupated 19 Nov; photographed 20 Nov, 18 mm + 6 mm proboscis; female emerged 2 Dec; 89/82A. 3, ventral view, near to emergence, collected by P.J.A. Cock as caterpillar on H. aristata, Nairobi, photographed 26 Oct 1988.

FIGURE 26. Caterpillar of Celaenorrhinus galenus opalinus parasitized by Apanteles (s.l.) sp. 1. Collected as n–4 on Hypoestes aristata, Karen, Nairobi, 29 Oct 1989; parasitoid larvae emerged from final instar, 17 Dec; photographed 20 Dec; 89/82C.

FIGURE 28. Celaenorrhinus galenus biseriata food plants. 1, Hypoestes forskaolii (identified as H. verticillaris white flower form), Shimba Hills (transplanted to Nairobi) 91.10.9. 2, H. forskaolii (identified as H. sp.?verticillaris pink flower form), Marere waterworks, Shimba Hills, 13 Dec 1990.