Spialia
Creators: name: Cock, Matthew J. W.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Lepidoptera
Hesperiidae
Spialia

description: Spialia discussion
As set out in the introduction to Spialia above (Table 1), De Jong (1978) grouped the African species into seven species groups. He was only able to consider adult characters and his proposed phylogeny is based on the male and female genitalia. The early stages of 11 species are now documented either here or by G.C. Clark (in Dickson & Kroon 1978), and listed in Table 1. They include representatives of six of the seven species groups of De Jong (1978). There appear to be some affinities between species based on the early stages, some of which align with De Jong’s species groups, but others don’t.
The pupae do not seem to offer useful characters except perhaps for the presence of brown plaques on the abdomen in some species. These are present in S. diomus (strong), S. colotes (weak), S. dromus (strong), S. ploetzi (strong), and S. zebra (weak), but not, or at least not discernably, in S. kituina and S. spio. I cannot make out any signs of these plaques in the plates of G.C. Clark (in Dickson & Kroon 1978), but they are not drawn at sufficient magnification to conclude that they are not present in any of the species he dealt with. The significance and function of these structures is unknown to me. Similarly the significance of the dimorphism of placement of the upper row of plaques best observed in S. zebra bifida, but also found in S. colotes transvaaliae and potentially found in other species, is unknown. These plaques are superficially reminiscent of the structures noted on the pupa of Gretna cylinda (Hewitson) (Cock et al. 2016, Figure 37), but the positioning and number per segment is different in this example, so this may not be a valid parallel.
Next I consider the similarities within De Jong’s (1978) species groups, particularly where the early stages of more than one representative are known. For the asterodia group, we have information and illustrations for the early stages of all three species: S. asterodia (Dickson & Kroon 1978, plate 13), S. agylla (Henning et al. 1997, pp. 100–101), S. kituina (Figures 2–5). The ova of S. asterodia and S. kituina are very different: the former with regular relatively low ribs and clear transverse ridges between the ribs, and the latter (assuming it is correctly associated; see text above) with thick, heavy interrupted ridges. Henning et al.’s (1997) description of the ovum of S. agylla, ‘pale greenish blue with white ribbing’, is not clear enough to interpret in this context. Henning et al. (1997) describe the final instar caterpillar of S. agylla as greyish brown, so the photo of a reddish caterpillar is probably of one about to pupate. Apart from this, the bodies of the caterpillars of all three species appear quite similar, with short, pale, erect setae, and an unusual uniform brown or transparent pronotum lacking the usual black and pale markings. There is little detail visible of the head in the image of S. agylla in Henning et al. (1997), but it can be seen that the setae are short, without obvious long black setae. The heads of S. asterodia and S. kituina have rather different vestiture: S. asterodia has short white clubbed setae, longer, clubbed, truncate, setae darker apically, and scattered long black, erect, flexible setae which may be barbed, whereas S. kituina has short, pale, recumbent, aciculate setae, and long, erect, simple setae, mostly pale, but some of which are dark dorsally and laterally.
For the spio group, we have details and illustrations for all three species: S. spio (Figures 8–10; Dickson & Kroon 1978, plate 16, Henning et al. 1997, pp. 112–113), S. diomus (Figures 12–13) and S. ferax (Dickson & Kroon 1978, plate 15, Henning et al. 1997, pp. 114–115). The ova of all three species have uniform regular ribs, but the caterpillars of S. spio appear very different to those of S. diomus and S. ferax with regard to the pronotum colour and markings and head vestiture, so much so that they appear more similar to caterpillars from other species groups than to each other— S. spio resembling the colotes group and S. diomus and S. ferax the dromus group.
We have no detailed information on the biology of S. doris, the single member of the phlomidis group found in sub-Saharan Africa, but the distinctive caterpillar of the European species S. phlomidis (Herrich-Schäffer) which feeds on Convolvulaceae, has a dark head, orange-brown pronotum, and grey body with large black subdorsal spots T2– A 9 (Wagner 2015). There is information and illustrations available for only one of the two species of the colotes group: S. colotes (Figures 16–18). For the sertorius group, we have information and illustrations for S. mafa (Dickson & Kroon 1978, plate 17), the Indian S. galba (Figure 1), and there is information and illustrations available for the European S. sertorius (Hoffmansegg) (Pro Natura 1999, Wagner 2015), S. orbifer (Hübner) (Wagner 2015, Tikhonov et al. 2015) and S. therapne (Rambur) (Wagner 2015). The three European species feed on Rosaceae and have a dark head, orange-brown pronotum, dark (S. sertorius, S. orbifer) or speckled brown (S. therapne) body, with a dorsolateral yellow line (S. sertorius, S. therapne) or row of spots (S. orbifer). The European species are very different from the African S. mafa, which may be linked to their different food plant family.
For the dromus group, we have details and illustrations for two of the five species: S. dromus (Figures 21–22; Dickson & Kroon 1978, plate 14) and S. ploetzi (Figures 24–25). The ovum of S. ploetzi has not been documented, but the caterpillars of the two species have a lot in common: both have conspicuous black linear setae and both have two pairs of round brown plaques on the upper adfrontals. The pupae of both species have oval brown plaques on the pupa abdomen, in common with several other species. Accordingly, the early stages offer good support for the affinity of these two species.
We have details and illustrations for three of the six species of the delagoae group: S. nanus (Dickson & Kroon 1978, plate 11, Henning et al. 1997, pp. 92–93), S. zebra (Figures 27–29) and S. sataspes (Dickson & Kroon 1978, plate 12). The ova of S. nanus and S. sataspes are ribbed slightly irregularly, whereas the ribbing of that of S. zebra (if correctly associated) is very irregular, with interrupted ridges and cones. The caterpillars of S. nanus and S. sataspes seem quite similar, with very short inconspicuous setae on the body, the pronotum marked in dark and pale rectangles, and the head covered with short aciculate setae, dark in S. nanus and pale in S. sataspes, with a few longer black setae. The caterpillar of S. zebra differs in having longer, more conspicuous setae on the body, white densely aciculate setae on the head, slightly longer pale or dark simple setae, but no obviously longer dark setae. The three species form a plausible, although not convincing group.
Next, are there general similarities or differences that cut across species groups and support or contradict the phylogeny of De Jong’s (1978) species groups? The nine known ova can be divided into three groups: those with regular ribs for at least the basal two-thirds: S. spio, S. diomus, S. ferax, S. mafa mafa and S. dromus, those with irregular ribs: S. asterodia, S. colotes and S. zebra, and those of intermediate form: S. nanus and S. sataspes. Of the first group, the ova of S. dromus differ in that the dorsal third, the sculpture is broken up into irregular ridges. These groups do not align with De Jong’s (1978) species groups.
The caterpillars, and in particular the vestiture of the head are quite varied. Four of the species treated have conspicuous black linear setae: S. diomus (Figure 12), S. ferax (Dickson & Kroon 1978, plate 15), S. dromus (Figure 21.2–3; Dickson & Kroon 1978, plate 14) and S. ploetzi (Figure 24.2–3). Spialia diomus (Figure 12.3) and S. ferax (Dickson & Kroon 1978, plate 15) have fan-like scales covering the face, which are not found in the other two species. Based on these characters, it seems reasonable to postulate that S. diomus, S. ferax, S. dromus, and S. ploetzi are part of one lineage (evenly ribbed ova, linear scales on head, brown plaques on pupa), and that within this, S. dromus and S. ploetzi are closely related, as are S. diomus and S. ferax (as noted above). However, De Jong’s (1978) phylogeny indicates no close relationship between S. diomus and S. ferax and the dromus group. Other characters of the caterpillars do not suggest obvious groups. The lack of clear patterns may be seen to support De Jong’s (1978) conclusion that Spialia spp. can be divided into a relatively large number of species groups, some with rather few representatives.
description: Published as part of Cock, Matthew J. W., 2016, Observations on the biology of Afrotropical Hesperiidae (Lepidoptera) with particular reference to Kenya. Part 10. Pyrginae, Carcharodini, pp. 301-350 in Zootaxa 4173 (4) on pages 337-338, DOI: 10.11646/zootaxa.4173.4.1, http://zenodo.org/record/256597