Metisella willemi Wallengren, 1857

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 : 502-503

Metisella willemi Wallengren, 1857

Originally described from Kaffraria (Natal) the range of this species extends from South Africa to DR Congo and East Africa, with one record from Somalia ( Evans 1937). This seems to be a very localised species, but where it does occur, it is not rare. Thus for a while it could be found regularly in the grounds of the Kisii Hotel , Kenya, in the late 1980s. Here parts of the grounds had been neglected for some years and only cut back in patches at intervals. The resultant mixture of vegetation included a scattering of the food plant, Setaria megaphylla (= S. plicatilis ), growing amongst other vegetation up to one metre high, and partially shaded by large trees. Unfortunately, on MJWC’s last visit (February 1991), almost the whole area had been cut back, and the grounds are now set to lawns (http://kisii-hotel.awardspace.info/index.htm) and far less interesting entomologically. What was particularly attractive about S. megaphylla in the Kisii situation is not clear ; MJWC has seen similar sites with S. megaphylla in the more open parts of Kakamega Forest , but never found M. willemi there.

Adult behaviour. The adults are weak fliers and settle frequently on grass stems with their wings closed (Figure 18.2). Cooper (1973) associates this species with open bush in Zimbabwe, where it can be locally abundant and notes that ‘it has a low flight and seeks shady grassy spots where it settles on low shrubs, grass or sometimes on the ground’. The adults will also drink at wet places ( Kielland 1990).

Food plants. Sevastopulo (1975) lists the food plants as grasses generally. Kielland (1990) and Larsen (1991) repeat this and the latter adds MJWC’s record from Setaria . We assume this is the source of the same food plant record in Henning et al. (1997) and Woodhall (2005). The caterpillars which MJWC found at Kisii were all on Setaria megaphylla , and we anticipate that this species may be selective as to which species of grass it will use for oviposition.

Leaf shelters. The shelters are formed in the apical part of the leaf, by rolling the leaf downwards, and feeding is from the edges of the same leaf, basal to the shelter, so that the basal portion of the leaf is positioned normally. A first or second instar caterpillar made a shelter from the apical 20mm of a 15 cm leaf. Large caterpillars will completely bare the midrib so that the shelter hangs by it like a stalk.

Caterpillar. The early instars are green with a dark head. The penultimate instar (Figure 19.1–2) is 8mm when newly moulted. Head 1.25 x 1.4mm wide x high; matt, rugose; translucent dull green, epicranial and adfrontal sutures narrowly dark or black, a wider line from vertex, over apex to top of stemmata; posterior margin narrowly dark, in one case with an adjacent small diffuse dark patch laterally; scattered short, pale, semi-recumbent setae. T1 with a dark dorsal spot and another below each white dorsolateral line. Body pale, slightly yellowish green; distinct subdorsal and dorsolateral lines, the latter extending onto T1; diffuse pale lateral line; short pale setae.

The final instar (Figure 19.3–4) grows to at least 20mm, with a distinctive dull brownish green head, 1.9 x 2.4mm wide x high (n=4). Based largely on 89/8B, the head is pale brownish green, paler down centre of face; matt, rugose; scattered short, pale, semi recumbent setae. T1 concolorous with body. Body dull green; white subdorsal line T1– A 9, slightly diffuse, especially on lateral margin; distinct white dorsolateral line T1– A 9; a rather diffuse, greenish white lateral line; spiracles and connecting line of trachea visible through cuticle pale, inconspicuous; body covered with scattered short, pale setae.

Pupa. The pupa ( Figure 20 ) is similar to others of the genus and formed in the last leaf shelter. Individual 89/ 8 A was 21mm long, frontal spike 2.3mm long, 1.3mm wide at the base, slightly upturned at the tip; smooth; pale whitish green, with dark dorsal line from tip of spike to cremaster, bordered by distinct white subdorsal and dorsolateral lines, and a diffuse lateral line. The cuticle is transparent and the pupa takes the colour of the developing adult, completing development in 10–15 days.

Figures

FIGURE 20. Pupa of Metisella willemi, dorsal view; collected 21 Feb 1989 on Setaria megaphylla, Kisii; pupated 25 Feb; photographed 26 Feb; adult female 7 Mar; 21 mm; 89 / 8 A.