Gorgyra bibulus Riley, 1929

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 : 7-10

Gorgyra bibulus Riley, 1929 (in Eltringham et al. 1929)

This localised species was described from the slopes of Mt Kenya ( Eltringham et al. 1929) and is also found in Tanzania ( Kielland 1990) and Uganda ( Evans 1937). However, the specimens reported from Nigeria by Evans (1937) are from Cameroon ( Larsen 2005). It is found in forests, highland forests and forest margins and adults settle on low vegetation and flowers according to Kielland (1990).

Food plants

Van Someren (1974) recorded the food plant as Drypetes gerrardii in East Africa; at that time Drypetes was placed in Euphorbiaceae , but it is now placed in Putranjivaceae . This record is repeated by subsequent authors ( Heath et al. 2002), or simplified to Drypetes ( Sevastopulo 1975, Larsen 1991, Ackery et al. 1995). In the 1990s, ABRI collectors discovered that Rourea thomsonii (Connaraceae) is a food plant in Gatamayu Forest, Kenya ( Figure 5 ), and the early stages that MJWC collected there with an ABRI collector on 4 Jul 1998 (98/201) are described and illustrated below. Probably, this ABRI food plant record is the origin of the record of R. thomsonii in Heath et al. (2002). The record from Drypetes gerrardii has not been repeated since Van Someren (1974), and the possibility of a misidentification or error cannot be discounted.

Leaf shelters

The stage 1 and stage 2 shelters ( Figures 5 and 6.1 ) are two-cut shelters from edge of the leaf; the shelter lids are broad, the two cuts being at right angles to the leaf edge, so that the bridge is as wide as the shelter, and the resultant flap is folded under.

One stage 2 shelter measured 20 x 7mm with a 13mm penultimate instar (98/201D); the shelter lid was raised from the leaf by pulling the two narrow ends together with silk. Another stage 2 shelter contained a 14mm penultimate instar caterpillar ready to moult (98/201E; Figure 6.1 ); one end of the shelter was closed but not sealed.

Two final instar caterpillars were field collected. The smaller 19mm caterpillar (97/201C) was in a shelter made on a 100mm leaf using the distal half, a large flap having been folded under; most of the feeding was basal to the shelter and the midrib was completely bare for 15mm immediately basal to the shelter ( Figure 6.2 ). The shelter of the larger, 20mm caterpillar (98/201B) was clearly an earlier version of the pupal shelter described below. On a leaf of 65mm, the basal 27mm had been folded over upwards, and most of the leaf distal to this had been eaten (or cut off). The caterpillar pupated on 12 July, eight days after collection, so this shelter seems to have been constructed during the final instar for pupation.

A pupal shelter found in the field ( Figure 6.3 , 98/201A) was formed in a leaf originally 45mm long, which had become dead and brown because of the caterpillar’s feeding. The distal half of the leaf was eaten (or cut off) except for the midrib and a few scraps; the basal half was folded over upwards along one side of the midrib until flat, forming a shelter 22mm long; the portion along the midrib formed a tube; strands of tough brown silk along the edge of this tube held the shelter together; the basal end of the tube was sealed shut, and the distal end had a round exit hole lined with silk; the inside of the tube was lined with silk and covered with white waxy powder which was also on the pupa; an adjacent leaf was also heavily eaten or cut back, dead and brown, and the remaining 25 x 15mm portion dangled alongside the pupal shelter, but this may have been fortuitous rather than normal.

Ovum

Oviposition is concentrated on the youngest red-green flush leaves. At this stage the leaves are still folded in half along the midrib, and the ova are inserted between the two halves of the leaf, some at the margin, but others well inside. The ovum is stuck to one half of the leaf by its base, and to the other at the micropyle. Several ova can be found close together. Hence, for example, one clump of about ten flush leaves on a regenerating cut branch had nine caterpillars in stage 1 shelters ( Figure 5 ). The ovum ( Figure 7 ) is white, about 0.77mm (n=4) in diameter, 0.41mm high (n=2), it is flattened dorsally and widest a little above the base. It is finely sculptured with horizontal rows of adjacent polygonal pits extending almost to the micropyle, about 50 in total around the circumference where the ovum is widest. About half the shell of the ovum is eaten by the newly hatched caterpillar.

Caterpillar

The first instars are green with a black head, 1.04 x 0.96mm wide x high (n=6) in instar n-2. In the penultimate instar (98/201D, Figure 8 ) the head is blackish, rugose, oval, slightly wider basally, slightly indented at vertex, 1.63 x 1.46mm wide x high (n=3); T1 concolorous; body green with diffuse pale subdorsal lines; faint brown semicircular mark on anal plate; spiracles pale, inconspicuous; legs concolorous. The newly moulted penultimate instar measured 8mm (98/201J), and a premoult caterpillar (98/201E) measured 14mm.

The final instar caterpillar is similar to earlier instars. Based on individual 98/201B ( Figure 9 ): 20mm; head oval with slight indentation at vertex, 2.2 x 2.71mm wide x high (n=1), brown, posterior margin black, rugose; T1 concolorous; body yellow-green, more yellow in transverse folds at posterior of each segment, darker green dorsal line; T1–T2 more slender than following segments; anal plate with weak quadrate reddish mark; spiracles pale, inconspicuous; legs concolorous.

Pupa

The pupa ( Figure 10 ) is supported by the cremaster and a weak, vestigial silk girdle; 18mm long; matt, dark brownblack; wing cases brown; a bifurcate frontal projection; proboscis extends 1.4mm beyond wing cases (98/201D); pupa covered with very short, pale setae, which are longer on the anterior and posterior parts of the eye. A male ( Figure 4 , 98/201B) completed pupation in 16 days.

Natural enemies

A 7mm n-2 instar caterpillar in a stage 2 shelter (98/201H) was dead, together with four euplectine larvae, which had become black naked pupae by 11 July and adults emerged 16 July. The field collected pupa (98/201A) was parasitized by a large (8.6mm) ichneumonid (predominantly yellow, abdomen brown; head, forecoxa, and central dorsal part of thorax black; hind tarsi dark) which emerged on 22 Jul, 18 days after collection.

Figures

FIGURE 4. Adult male Gorgyra bibulus, collected as final instar caterpillar 4 Jul 1998 on Rourea thomsonii, Gatamayu Forest, Kenya; adult 28 Jul, 98/201B.

FIGURE 5. Rourea thomsonii, a food plant of Gorgyra bibulus with feeding and leaf shelters (arrows), Gatamayu Forest, Kenya, 4 Jul 1998; 98/201M.

FIGURE 6. Leaf shelters of Gorgyra bibulus on Rourea thomsonii, collected 4 Jul 1998, Gatamayu Forest, Kenya; the lines in the background are 8mm apart. 1, stage 1 shelter on left, 98/201E; stage 2 shelter on right, 98/201F; 2, stage 3 shelter, 98/201C; 3, pupal shelter, 98/201A.

FIGURE 7. Ovum of Gorgyra bibulus, on leaf of Rourea thomsonii, Gatamayu Forest, Kenya, 4 Jul 1998, 98/201K. 1, as laid in a folded very young leaf; 2, dorsal view with part of the facing leaf surface adhering on top.

FIGURE 8. Penultimate instar caterpillar of Gorgyra bibulus, collected 4 Jul 1998 on Rourea thomsonii, Gatamayu Forest, Kenya; photographed 4 Jul; 13mm; 98/201D. 1, dorsal view; 2, detail of head.

FIGURE 9. Final instar caterpillar of Gorgyra bibulus, collected 4 Jul 1998 on Rourea thomsonii, Gatamayu Forest, Kenya; photographed 4 Jul. 1, dorsal view, pupated 13 Jul; 19mm; 98/201C; 2, detail of head, 4 Jul; pupated 12 Jul; 20mm; 98/201B; 3, dorsal view, as 2.

FIGURE 10. Pupa of Gorgyra bibulus, collected 4 Jul 1998 on Rourea thomsonii, Gatamayu Forest, Kenya; photographed 4 Jul; parasitized; 18mm; 98/201A.