New to nature No 112: Lichenagraecia cataphracta

This brilliant lichen mimic's spiny legs set it apart from all other Australian katydids


L cataphracta is a lichen mimic and, like other katydids, has a
species-specific song

A truly remarkable new genus and species of katydid, Lichenagraecia cataphracta, was described last year from a small number of locations in northern Queensland by David Rentz and co-authors You Ning Su and Norihiro Ueshima.

Katydids in general are recognised as masters of disguise. Many are uniformly green in colour with wide leathery forewings, the tegmina, which are not only leaf shaped in outline but have ribs resembling the veins in leaves.

The new species, however, goes one better, looking like a lichen-encrusted branch in amazing details of structure and colour. Even though the species is difficult to spot sitting among actual lichens, it occurs in areas heavily collected by entomologists and would surely have turned up sooner were it found in the understorey. Thus, the authors suspect that it may live instead high in the treetops.

Although superficially unique, on closer examination, it seems obvious that its spiny and lichen-like body is merely an extreme variation of a known theme. Ignoring its spiny surface, the pronotum resembles closely that of two related genera, as do the genitalia. In fact, the authors posit a new tribe to accommodate the three genera. The other two, Kapalgagraecia and Armadillagraecia, share with Lichenagraecia shortened wings, a saddle-shaped pronotum with spines at least around the margins, protruding round eyes sitting high on the head and unarmed ovipositors, among other characters. These genera are also Australian endemics and are found in the Northern Territory, northern Western Australia and western Queensland. The spiny legs of the new genus and species set it apart from all other Australian katydids.

There are many times when speculations about the adaptive significance of weird anatomical structures seem a bit fanciful. This is not one of them. One look at L cataphracta and it is impossible not to conclude that it is a lichen mimic and an amazingly convincing one at that.

As is often the case with newly discovered species, we do not yet know much about its biology. This is a good excuse to summarise a bit about katydids in general.

The family tettigoniidae includes the katydids as well as bush crickets and long-horned grasshoppers. Beyond their impressive mimicry, katydids are equally well known for their night-time serenades. Their songs are often so species-specific that they can be used for accurate field identifications, just as in birds. With more than 6,000 species worldwide, they are nearly as numerous as birds. Stridulation is accomplished by males when a file on one wing is rapidly rubbed over a scraper on the other.

Most katydids are nocturnal, resting during the day, and herbivores feeding on leaves, twigs and sometimes seeds. A smaller number are predators or ominivores. While quite a few insects have hearing organs called tympana consisting of thin, tight membranes, these are the only insects that have their "ears" on their front legs.

The senior author is pre-eminent in the world of katydids and entomology. David Rentz was for a quarter-century curator of orthopteroid insects in the CSIRO National Insect Collection in Canberra. While a great deal remains to be learned about the katydid fauna, a first-rate source for more information on species down under is Rentz's A Guide to the Katydids of Australia, a Whitley book award winner in 2011 in the "field guide" category.

In the Queen's birthday honours list this year, Rentz was appointed a Member of the Order of Australia.