Metisella quadrisignatus nanda Evans, 1937

Cock, Matthew J. W. & Congdon, T. Colin E., 2017, Observations on the Biology of Afrotropical Hesperiidae (Lepidoptera) with particular reference to Kenya. Part 11. Heteropterinae, Zootaxa 4226 (4), pp. 487-508 : 498-499

Metisella quadrisignatus nanda Evans, 1937

Evans (1937) described this subspecies from Kenya (Escarpment, 1980m [6,500 ft.]) and its range is restricted to the Central Highlands of Kenya . The nominate subspecies, quadrisignatus Butler, 1894 is smaller with reduced spotting, and was described from Zomba ( Malawi) and is also recorded from Tanzania ( Evans 1937).

The four orange spots on the fore wing upper side make this species distinctive. Specimens with reduced spotting are not rare; MJWC has one with only the spot in space 7 remaining and a few orange scales at the other spot positions. The hindwing upper side orange markings are also variable in extent and although the submarginal band may be absent, the cell spot is usually present. Even specimens with reduced spotting are unlikely to be confused with M. trisignatus (Neave) as that species never has a trace of a cell spot on the fore wing upper side. There is little sexual dimorphism, except that the presence of an orange spot in space 1B F is perhaps more common in females.

This subspecies is quite common in forests of the Central Highlands, particularly around Nairobi. It also occurs in the Chyulu Hills , where it is common in the borders of forests to 1980m (6,500 ft.) ( Van Someren 1939).

Adult behaviour. It flies low along tracks and margins of woods, sometimes extending to hedgerows with trees. As with others of the genus it rests with its wings open when sunbathing (Figure 12.1) and otherwise with its wings closed. It occasionally visits flowers, when it is an easy prey for crab spiders (Figure 12.2), perhaps because it is a relatively weak skipper species.

Food plants. Larsen (1991) correctly anticipates that the food plants are ‘almost certainly various grasses’. Along forests tracks at Muguga, NW of Nairobi, MJWC believes the food plant is Cynodon nlemfuensis ; this identification however was based on flowering specimen from Nairobi, since this grass was not found in flower at Muguga. MJWC has not found caterpillars easy to locate and has not found them in other forests around Nairobi where M. quadrisignatus is common. Zenonia zeno occurs on the same food plants in the same areas as M. quadrisignatus , and the early instars (green with a black head) were not distinguished.

Leaf shelters. A final instar caterpillar (88/107B) made a shelter from a leaf blade, pulling the edges of the central portion downwards and holding them with silk; feeding truncated the leaf blade distal to the shelter.

Caterpillar. Observations were made on the final and penultimate instars (88/107), but earlier instars were not reared through and would not have been distinguished from similar stages of Z. zeno and other Baorini .

The penultimate instar (Figure 13.1, 88/107D, E) grew to 15mm; head 1.4 x 1.7mm wide x high; pale green, with narrow brown stripe along epicranial and adfrontal sutures, and broad brown stripe from apex to stemmata; pronotum narrow, dark; body yellowish green with pale subdorsal and dorsolateral lines; conspicuous black near rectangular mark on anal plate.

The final instar (Figure 13.2–3, 88/107B) grows to 23mm; head 1.8 x 2.3mm wide x high, matt green with brown stripe from apex, anterolaterally to stemmata, widest in middle; T1 concolorous with body; body smooth, but corrugated at intersegmental areas; pale whitish green; dorsal line defined by a pair of weak, diffuse, white subdorsal lines; strong, narrow, white dorsolateral line T1– A 9; trace of a diffuse line laterally; anal plate green. Individual 89/107E differed in that the broad stripe on the head was dark, almost black (cast head capsule in Figure 14 ), and the posterior margin of the head was narrowly dark.

Pupa. The pupa ( Figure 14 ) is typical of the genus and formed in the last leaf shelter. Individual 88/107E ( Figure 14 ) measured 18mm long, including 2.0mm frontal spike; dull light green, becoming paler with age; obscure faint, dark dorsal line from tip of frontal spike to cremaster; angles dorsolateral line from above eye; white subdorsal line from near front of T2 to about 2mm short of cremaster; black dots on T2 and T3 adjacent to hind wing. The pupa takes 12–13 days to complete development.

Figures

FIGURE 14. Dorsolateral view of pupa of Metisella quadrisignatus nanda collected 31 Oct 1988 on Cynodon nlemfuensis, South Muguga Forest, NW of Nairobi; pupated 16 Nov; photographed 16 Nov 88; adult female 29 Nov; 18 mm; 88 / 107 E.