Artitropa milleri coryndon Evans, 1937

Cock, Matthew J. W., Congdon, T. Colin E. & Collins, Steve C., 2015, Observations on the Biology of Afrotropical Hesperiidae (Lepidoptera). Part 8. Hesperiinae incertae sedis: Dracaena Feeders, Zootaxa 3985 (3), pp. 301-348 : 315-316

Artitropa milleri coryndon Evans, 1937

Based on material from Nairobi, Evans (1937) named subspecies coryndon after the Coryndon Memorial Museum (now National Museums of Kenya, NMK), where the type is held. This subspecies was reported to be restricted to the Central Highlands of Kenya, and there are specimens from Mt. Kenya (1830m, 6000 ft.) in the BMNH. It has been recorded recently from Kakamega Forest, western Kenya ( Kühne et al. 2004), but we refer to this population as A. milleri SCC01(Kakamega) below. It was described from Nairobi, and Larsen (1991) says it is not uncommon there.

MJWC has found caterpillars of this subspecies at Thika (at about 1500m, on the same plants as A. erinnys vansomereni ) and Tigoni (about 2130m), but not in Nairobi itself (about 1660m), where he found only A. erinnys vansomereni . Similarly, in the Van Someren collection in the BMNH accessions there are just three specimens from Ngong, but none from Nairobi. SCC has reared it from Nairobi, Kibirigwe (Nyiiri) and Meru; it was commoner than A. erinnys vansomereni at Meru. V.G.L. Van Someren reared this species and although he did not document the early stages, material was available to Evans (1937) when he described ssp. coryndon.

Food plants. As discussed under ssp. milleri above, Van Someren (1974) lists D. mannii (as usambarensis ) as the food plant of A. milleri ‘and subspecies’, but it is not clear whether this is based on one or both subspecies. Given that Van Someren reared A. m. coryndon , and there are no specimens of A. m. milleri in his collection (BMNH accessions), we assume this record should be referred to A. m. coryndon . Larsen (1991) indicates the food plants are Dracaena including D. steudneri in the suburbs of Nairobi. SCC has also reared it from D afromontana in high Meru, Kenya.

Ovum. Working in Kenya, MJWC did not distinguish the ova from those of A. erinnys vansomereni , although examination of preserved material suggests that the ova are indistinguishable. The newly hatched caterpillar eats the shell of the ovum except for the base.

Leaf shelters. The young caterpillars make leaf rolls similar to those described for A. e. vansomereni below; when young caterpillars of the first three instars were collected together at Thika, neither they nor their shelters were distinguished (although examination of preserved material shows that the third instars although similar can be distinguished). The pupal shelter was a large flap rolled under from the edge of the leaf, with a vertical silk screen just in front of the pupa.

Caterpillar. Examination of preserved remains indicates that there are normally five instars, and so they are recognised as such here. The heads of instars 2 to 5 measured 1.04 x 1.15 (n=7), 1.44 x 1.60 (n=8), 2.19 x 2.47 (n=15), and 3.42 x 3.95 (n=7) mm wide x high. Instar 2 has a plain dark head. The head of the instar 3 caterpillar is dark, with a diffuse brown marking on the face, which outlines dorsally and laterally a more or less heart-shaped dark marking in the centre of the face. This heart shaped marking is variable in size and clarity, measuring 0.9 (range 0.78–1.10) x 0.83 (range 0.75–0.98) mm wide x high (n=7).

A fourth instar caterpillar (88/52B1) measured 20mm when described six days before moulting. Head 2.1 x 2.4 mm wide x high; light brown with dark markings; posterior margin broadly dark to edge of face; heart- or V-shaped marking in upper 2/3 of face, bordered, except at ventral point, with a very light brown margin; stemmata dark with dark spot anterior to them. Pronotum on posterior margin; narrow, black, stopping short of spiracles; body dull grey-green, with narrow, pale lateral line where trachea visible through cuticle; paler below this; anal plate translucent; male gonads yellow, conspicuous; spiracles inconspicuous; all legs concolorous. The size of the head varies from 1.92–2.35 x 2.24–2.67mm wide x high in 15 individuals. The markings also vary, the central heart or V-shape was on average 1.40mm wide, but varied from 0.98 to 1.57mm, and on average was 1.39mm high but varied from 1.10 to 1.96mm; the shape of the dorsal notch varied from a narrow V to a U-shape to a square sided shape.

The mature caterpillar ( Figure 12 ) is a little smaller than that of A. erinnys vansomereni , which overlaps with A. m. coryndon in distribution; on average the head capsule of vansomereni measures 3.66 x 4.41 mm wide x high, whereas that of coryndon measures 3.42 (range 3.14–3.65) x 3.95 (range 3.88–4.08) mm (n=7). As Evans (1937) noted when comparing A. m. coryndon and A. e. vansomereni ‘the early stages have been found to be remarkably different’ and this particularly applies to the final instar caterpillars ( Figures 12 and 26 ). The head capsule of ssp. coryndon is orange-brown with black markings. Typically, these comprise: posterior margin narrowly dark; an transversely elongate postero-dorsolateral spot, a lateral spot, a diffuse postero-ventrolateral spot, a dark line through the anterior stemmata, a spot midway between this line and the adfrontals, and a conspicuous and distinctive rounded V-shaped mark on the face, typically with the black area in the frons separated from the black area in the adfrontals by a brown line. Individuals may be more heavily marked: the lateral spots may merge into a continuous irregular lateral band, extending as far anteriorly as the stemmata; the spot between the stemmata and adfrontals can be larger; the base of the V may be more or less continuous with the black marking of the frons. Individuals may also be more lightly marked: the lateral spots may be smaller, and the postero-ventrolateral spot may be absent; the black marking on the frons may be reduced to a short narrow central line. The pronotum is marked with a narrow black line on the posterior margin, widened into a spot laterally. Body greenish white; anal plate unmarked, translucent; spiracles pale; all legs concolorous. The wax glands are distributed ventrally on A1– A8, as for A. erinnys vansomereni below. The fifth instar is completed on average in 15 days (range 13–17).

Pupa. The pupa ( Figure 13 ) is similar in shape to those of other members of the genus. Pupa 88/51A from Thika measured 28mm without the proboscis, which projected a further 5mm beyond the cremaster. Four days after formation, the head and thorax were dark, a narrow dark dorsal line on thorax; abdomen whitish with a dark dorsal line (the pupa subsequently died so colouring may not have been typical); setae around T1 spiracle, anterior and posterior portions of the eye, and dorsally in small patch on T2. Pupa suspended in the pupal shelter by a multistranded silk girdle just behind the thorax, not engaging dorsal setae on T2; both the pupa and the inside of the shelter liberally covered with white waxy powder.

Other pupae were photographed (Figure 13.1–2); they are pale with a dorsal line on the thorax, and a heavier transverse line dorsally between the eyes (Figure 13.2), neither of which are present as strongly in other members of the A. milleri complex. The pupa takes an average of 20 days (range 18–21) to develop.

Natural enemies. At Thika, A. milleri coryndon and A. erinnys vansomereni occur together, but the ova could not be separated and the caterpillars could only be separated from the third or fourth instar onwards. A third instar A. milleri coryndon caterpillar (MJWC 88/52C) was attacked by a gregarious ectoparasitoid, identified by J. LaSalle (CABI) as Pediobius sp. afronigripes group ( Eulophidae ). There were ten naked black pupae in the leaf shelter of the host, from which six females and four males emerged. At the time, the parasitoid pupae were not distinguished from those of Elasmus sp. ( Eulophidae ) which was reared from A. erinnys vansomereni . It is likely that both parasitoid species will attack both Artitropa spp. Similarly Artitropa sp(p). ova at Thika were parasitized, but could not be sorted by species, and the resultant egg parasitoids are treated more fully under A. erinnys vansomereni below.

Figures

FIGURE 12. Final instar caterpillar of Artitropa milleri coryndon, collected on Dracaena steudneri, Thika, Kenya. 1 – 2, collected 22 Dec 1988; moulted to final instar 11 Jan 1989; photographed 16 Jan 89; pupated 27 Jan; 88 / 122 E; 1, head, lateral view; 2, head, anterolateral view. 3, anterodorsolateral view; collected 26 Jun 1988; moulted to final instar 12 Jul 1988; photographed 18 Jul, pupated 27 Jul; 88 / 52 B 3.

FIGURE 13. Pupa of Artitropa milleri coryndon, collected on Dracaena steudneri, Thika, Kenya. 1, dorsolateral view; collected 20 Dec 1988; prepupa 27 Jan 1989; photographed 14 Feb; emerged 17 – 20 Feb; 88 / 122; 2, anterodorsal view; collected as small caterpillar 26 Jun 1988; pupated by 29 Jul; photographed 16 Aug; adult 19 – 20 Aug; 88 / 52 B; 3, lateral view, shortly before emergence; collected as final instar caterpillar 26 Jun 1988; pupated 30 Jun; photographed 18 Jul; adult 20 Jul; 88 / 51 B.

FIGURE 26. Final instar caterpillar of Artitropa erinnys vansomereni, on Dracaena steudneri. 1, dorsolateral, anterior and posterior views; collected Thika, 2 Jul 1988; photographed 18 Jul; pupated 24 Jul, 88 / 52 A 1; 2, head, anterior view; collected Nairobi; photographed 13 Sep 1988; 88 / 75 A 1; 3, head with atypical light markings, anterolateral view; Nairobi, 17 Jan 2006 [TCEC]; 4, head with atypical dark markings, anterior view; Nairobi, 23 Dec 2002; 5, dorsolateral view, Nairobi; photographed 25 Nov 89; 89 / 94.