The Burlinius Head-hiders

Cryptocephalus (Burlinius) bilineatus, photographed by Josef Dvořák.

I may have to confess that, in direct opposition to the Deity, I am not overly fond of beetles. There are, quite simply, far too many of them, and even beetle families can be inordinately difficult to distinguish unless one is an expert (particularly the endless array of minute brown ones). Nevertheless, everything in beetles comes with an exception, and there are some groups that stand out: one of these is the leaf beetles of the Chrysomelidae. Chrysomelids are a highly diverse group, comparable to (though perhaps getting less press than) their close relatives the weevils and longicorns. They come in an enormous array of shapes and colours, and yet almost all (emphasis on almost) seem to carry an unmistakeable stamp saying, "I am a chrysomelid".

Cryptocephalus (Burlinius) pusillus, photographed by Amy.

The chrysomelid subgenus Burlinius of the genus Cryptocephalus includes over 120 species found across the Palaearctic region, with a single species known from the Simien Mountains of Ethiopia (Schöller 2002). The name Cryptocephalus means 'hidden head', and refers to how, when the beetle is viewed from above, the head is usually hidden underneath the pronotum. Species of Burlinius are relatively small with regular lines of punctures on the elytra, but are primarily distinguished from other Cryptocephalus species by the morphology of the male genitalia. The aedeagus (the intromittent organ) bears a dorsodistal appendage covering the dorsal opening, and two symmetrical ventral processes (Erber & Schöller 2006). The external appearance of many Burlinius species is known to be quite variable, and genital morphology is also the best way of distinguishing many species (Warchałowski 1999).

Figures from Warchałowski (1999) showing variation in elytral patterning between individuals of Cryptocephalus jocularius.

As you might have guessed from the vernacular name 'leaf beetles', chrysomelids are generally herbivorous. Host plant records for Burlinius species indicate that they are often polyphagous, feeding on a wide variety of hosts. Burlinius species have been recorded from legumes, composite-flowered plants, spurges, even pines (Erber & Schöller 2006). Cryptocephalus and related taxa belong to a subgroup of the chrysomelids called the Camptostomata, in which the females have an array of chitinous pads called the kotpresse in the rectum (Schöller 2008). The kotpresse is used to encase the eggs when they are laid in a covering made from faeces and other secretions; when the larvae hatches, it uses this covering for protection and adds to it itself as it grows.

Hazel pot beetle Cryptocephalus coryli larva in its protective case, photographed by Roger Key.

REFERENCES

Erber, D., & M. Schöller. 2006. Revision of the Cryptocephalus-species of the Canary Islands and Madeira (Insecta, Coleoptera, Chrysomelidae, Cryptocephalinae). Senckenbergiana Biologica 86 (1): 85-107.

Schöller, M. 2002. The first representative of Cryptocephalus subgen. Burlinius Lopatin from tropical Africa (Chrysomelidae: Cryptocephalinae). Genus 13 (1): 33-37.

Schöller, M. 2008. Comparative morphology of sclerites used by camptosomatan leaf beetles for formation of the extrachorion (Chrysomelidae: Cryptocephalinae, Lamprosomatinae). In: Jolivet, P., J. Santiago-Blay & M. Schmitt. Research on Chrysomelidae vol. 1, pp. 87-120. Brill: Leiden.

Warchałowski, A. 1999. Übersicht der westpaläarktischen Arten der Untergattung Burlinius Lopatin, 1965 (Coleoptera: Chrysomelidae: Cryptocephalus). Genus 10 (4): 529-627.