Artitropa Holland 1896

Artitropa discussion

When Riley (1925) revised the continental African species, he did not examine the genitalia, working on wing pattern and to a limited extent on early stages. Evans (1937) seems to have accepted Riley’s conclusions and only added two taxa. For his revision, Evans seems to have dissected only one male of each species, and not dissected the different subspecies of A. erinnys and A. milleri. Thus he dissected a male A. e. erinnys from Zululand (within KwaZulu-Natal, South Africa) which is representative of the type locality (Port Natal) and a male A.m. milleri from Katanga, DR Congo, which is not representative of the type locality (Tukuyu, Tanzania). Further genitalia dissections are needed to assess the present classification and the status of the putative taxa recognised here. We suspect that A. milleri may comprise at least two species, milleri and coryndon, but perhaps more, but these have yet to be assessed based on their genitalia (T.B. Larsen in prep.) or by molecular methods.

The head markings of the caterpillars are more useful for separating species and species-groups, than for discriminating between subspecies of Artitropa. Thus, we can generalise that the caterpillars of A. comus, A. reducta and A. principetome are all very similar. Equally, there seem to be some differences between the caterpillars of the different populations / subspecies of A. erinnys and A. milleri, but our observations have not been sufficient to adequately document the degree and frequency of individual variation within populations. Our impression is that populations are generally quite consistent, but that atypical markings are not that rare. For example, we have reared A. erinnys vansomereni frequently, and although the markings are normally similar to the individual shown in Figure 26.2, individuals with much lighter head markings (Figure 26.3) and much darker head markings (Figure 26.4) were also documented. Again, the limited sample of three photographed individuals of A. erinnys comoranum (Figure 34) can each be matched up with a separate mainland population of A. erinnys.

We are well aware that several species co-occur in eastern Africa, so that just because the caterpillars of one species are found on a Dracaena sp. at a locality, it does not mean that nearby ova are of the same species. On one occasion, Ivan Bampton found three ova on one leaf of a large-leaved Dracaena sp. (steudneri or mannii) in deep shade in the Usambara Mountains, and raised a different species from each: A. milleri milleri, A. erinnys ehlersi and A. usambarae. This adds a degree of uncertainty to observations on the ova and early instars (and their natural enemies), which cannot be distinguished.

The caterpillars of several species have been shown to have the anal plate dark (Figures 26, 30, 37) or to have a double spot (Figure 9). Sevastopulo (unpublished) referred to the markings of the posterior portion of the caterpillar of A. erinnys and A. reducta resembling a lizard head, and TCEC has compared the markings of A. cama (Figure 9) to eyes. Janzen et al. (2010) have postulated that the conspicuous eye markings on the head of Hesperiidae caterpillars and pupa serve to frighten small insectivorous birds that may open leaf shelters. Given that many leaf shelters, including those or Artitropa spp., can be opened at either end, then it seems reasonable to suggest that anything that suggests a pair of eyes on the posterior end of the caterpillar could have a similar function.