Asteraceae

Abstract

Assuming this, I studied the interaction of Arctotheca calendula L. (Cape weed), a weedy daisy without dark markings on the ray florets, and the beetle Heterochelus sexlineatus Thunb., a herbivorous species with strong cutting mandibles. This plant species is visited by many hopliinid species (Scott & Way 1990) and I observed Heterochelus sexlineatus visiting at least seven other plant species at the study site, suggesting that there is only a diffuse relationship between the two study taxa.In Gorteria diffusa, the so-called beetle-daisy, the 'beetle' mark is a dark raised bump on the ray floret with a white spot in the middle and with yellow 'legs'. Under ultraviolet light this 'beetle' does not appear significantly different (pers. obs.). The number of 'beetles' per inflores cence is very variable (from none to a full ring with marks on all ray florets) within and between individuals (pers. obs.). The 'beetles' on inflorescences with a full ring appear to be the least derived condition because they are poorly differentiated and are similar in appearance to many other Asteraceae with a ring of conspicuous dark basal markings on ray florets (e.g. Gazania lichtensteinii). Even Arctotis species (e.g. A. gumbletonii Hook, f.), which Hutchinson (1946) suggested suffer more predation, have complex dark basal markings on the ray florets.It is thus possible that any dark marks near the base of the ray floret or darkening of the disc found in other genera such as Osteospermum, Dimorphotheca and Ursinia may be mimicking beetles. In the Still Bay area, J. Vlok and I noted an Ursinia species (close to U. paleacea (L.) Moench) which also appears to be a beetle-daisy. In this