Aethiopocassis quadrioculata (Coleoptera: Chrysomelidae: Cassidinae: Cassidini) and Platypria sp. Chrysomelidae: Cassidinae: Hispini)
This week we consider two interesting beetles, which I’ve named “4 roses” and “Spike”. Okay – the roses don’t really look much like roses, but the colour is perfect. “Spike” is an appellation that needs no explanation. It may not look it, but these two represent closely related groups of beetles, the Cassidini and the Hispini. Both tribes are in the subfamily Cassidinae, the members of which have specialized mouthparts and antennae that are placed next to each other, characters which both tribes share. The common name of the Cassidini is tortoise beetles and A. quadrioculata is an excellent example of a cassidine beetle’s shape (nearly circular when viewed from above) and of the fact that, with very few exceptions, the head of tortoise beetles is not visible from above. This arrangement places the head directly under the protective pronotum much as a tortoise might withdraw its head under its carapace when threatened.
Hispini is an old world (Africa, Europe, Asia) tribe and members are readily distinguished from the tortoise beetles by their shape (oblong, not circular) and by the head being visible from above. Some Hispini have evolved a successful defensive strategy, and it couldn’t be more different than that of their tortoise beetle cousins. In several genera of Hispini, adults are covered with an array of fixed spines probably meant to discourage attacks by potential pedators. The species of Platypria, such as the one in the accompanying image, are a good example. Although species of Hispini are quite small, their sharp spines can hurt even large mammals, such as humans, who try to pick them up.
The two tribes also differ markedly in the feeding behaviour of their larvae. Larval hispines are leaf miners, eating the plant’s mesophyll as they tunnel between the upper and lower layers of leaf tissue. In contrast, Cassidini feed in the open while moving over the leaf surface, each larva carrying a fecal shield composed of cast-off larval skins (exuviae), detritus, and excretions on the caudal appendage. The shield can be moved and is thought to provide physical protection against predators and parasitoids.