Anthia beetles mimicked by lizards

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Ecdysozoa > Panarthropoda > Tritocerebra > Arthopoda > Mandibulata > Atelocerata > Panhexapoda > Hexapoda > Insecta (insects) > Dicondyla > Pterygota > Metapterygota > Neoptera > Eumetabola > Holometabola > Coleoptera > Polyphaga > Family: Carabidae > Subfamily: Anthiinae

Adult Eremias lugubris lizards in southern Africa are cryptically coloured and blend with the red-tan colours of the Kalahari semi-desert.  However,  the juveniles are jet-black and white and very conspicuous and yet they forage freely and actively. While the adults'  movements are typically lizard-like, the juveniles move with stiff, jerky movements with their backs strongly arched and with the paler-coloured tails pressed to the ground. The lateral movements of the adults are not apparent in the juveniles. When juveniles change to adult colouration, the arch-walking behaviour is 'switched off'.

The conspicuous coloration and gait of the juveniles led the researchers to investigate how these young lizards survived predation. While the colour black is a thermoregulatory advantage for insects, it is not the case for reptiles in the desert and is a definite disadvantage when it comes to predation. The back-arching does not seem to be heat-avoiding behaviour as it is constant and is not limited to when the body temperature is high.

It was shown that the juvenile beetles' confidence rests in the fact that they are protected from predators because they mimic, in colour and behaviour, the notorious and noxious 'oogpister' beetles (genus Anthiinae, family Carabidae). Predators avoid the threat of the pungent, acidic fluid sprayed by these beetles when threatened or attacked. This unique mimicry by a terrestrial vertebrate of an invertebrate, is believed to be the first reported such case and seems to reduce predation on juvenile lizards. The mimicry is so effective that even the researchers confused the lizards for beetles when conducting their field work.

To evaluate how effective the mimicry was against predation, researchers examined the tails of various sympatric (occupying the same region) lizard species for evidence of damage and comparisons were made between  mimicking and non-mimicking, paler-coloured lizard species. The results showed that there were more damaged tails among the latter group than the mimicking group. It was also found that arch-backing juvenile lizards were avoided in 100% of interactions with snakes but were attacked if they moved normally. It was also found that the lizards' behaviour was different for different snakes. For a visual hunter, they remained immobile or arch-backed but for a snake that used only olfaction, they ran away at high speed.

Furthermore, the lizards' distribution overlaps with 15 species of Anthia and Thermophilum and it was found (by Schmidt) that as the juvenile lizards grow, their colour patterns change to match appropriately sized Anthiinae beetle species.