Field of Science

Anthaxia: More Modest Jewels

The jewel beetles of the Buprestidae are best known for their spectacularly patterned exemplars, a couple of which I've presented on this site before. But as with most animal groups renowned in this way, they also include their fair share of less immediately eye-catching members. The species of the genus Anthaxia are among these more modest jewels.

Anthaxia hungarica, photographed by Frayle.


Which is not to say they are unattractive. Anthaxia species still usually have the metallic gloss so widespread among the Buprestidae but they tend to be more uniform in colour, and those colours are often shades of bronze or blue-green rather than yellows or purples. They are also smaller than the species previously shown: a length of 6.5 millimetres would be relatively large for an Anthaxia. Some of the smallest species don't quite make it to three millimetres (Bílý & Kubáň 2010). Nevertheless, Anthaxia are incredibly diverse. Something in the range of 700 species are known from around the world (though they appear to be absent from Australia, with the single species described from Victoria now thought to have been based on a mis-labelled African specimen) and a quick Google Scholar search indicates new species continue to be described regularly. It should come as no surprise that many of these species would be difficult to distinguish without close examination.

Anthaxia scutellaris, a more colourful species of the genus, copyright Hectonichus.


Like other buprestids, Anthaxia species are wood-borers as larvae and flower-feeders as adults. The larvae seem to run the gamut of preferred tree hosts: Anthaxia have been found emerging from hosts ranging from pines to pears, from oleander to oaks. Some species appear to be quite catholic in their tastes: the recorded host list for the most polyphagous known species, A. millefolii, includes maples, chestnuts, carobs, oleanders, pistachios, plums, pears, oaks and rowans (Mifsud & Bílý 2002). Others are more discerning. Species of the subgenus Melanthaxia are only known to feed on conifers (Bílý & Kubáň 2010) and records for A. lucens indicate a dedication to stonefruit trees (Mifsud & Bílý 2002). Nevertheless, the larval hosts of many species remain unknown and there may be surprises. The North American species A. hatchi might be expected to be a conifer feeder like other Melanthaxia species but to date it has been collected in riparian habitats where conifers do not grow (Nelson et al. 1981). Could this member of an otherwise conifer-loving group have developed a taste for the willows and alders amongst which it lives? The question is yet to be answered.

REFERENCES

Bílý, S., & V. Kubáň. 2010. A study on the Nearctic species of the genus Anthaxia (Coleoptera: Buprestidae: Buprestinae: Anthaxiini). Subgenus Melanthaxia. Part I. Acta Entomologica Musei Nationalis Pragae 50 (2): 535–546.

Mifsud, D., & S. Bílý. 2002. Jewel beetles (Coleoptera, Buprestidae) from the Maltese Islands (central Mediterranean). Central Mediterranean Naturalist 3 (4): 181–188.

Ferreting up a Bird's Nose

Mites, as I may have commented before, seem to have an almost fractal level of diversity: the closer you look, the more there is of it. This is nowhere more apparent than when it comes to parasitic mites which infest almost any host in any way that you can imagine. For the subject of this post, I drew one such mite: the honeyeater nasal mite Ptilonyssus myzanthae.

Venter (left) and dorsum of female Ptilonyssus myzanthae, from Domrow (1964). The scale bar equals 500 µm.


Bird nasal mites of the family Rhinonyssidae are, as their name indicates, inhabitants of the nasal passages of birds. General adaptations of the family for their parasitic lifestyle include tendencies towards reduction of the body sclerotisation and reduction in the length and number of setae. They use the claws on their front legs to tear openings in the host's mucous membranes and then feed on its blood. Transmission of nasal mites seems to happen during bill-to-bill contact such as when parents are feeding their young or during mating activities, or indirectly through water or on the surface of perches or the like. Rhinonyssid nasal mites are not known to transmit any actual diseases between hosts but they can cause the formation of lesions or inflammation or the like. All in all, probably not very pleasant for the bird (see here for some more details).

Whole-body illustration of a different rhinonyssid species, from Greg Spicer.


Nevertheless, infection rates in bird populations can be very high and most (if not all) bird species will be host to some nasal mite species. Most species of nasal mite are very host specific, known on only one or a few bird species (it must be noted, though, that the question of just how many researchers choose to look up a bird's schnozz in search of mites may not be irrelevant here). Ptilonyssus myzanthae was described by Domrow (1964) from two species of honeyeater in Queensland, Australia: the noisy miner Manorina melanocephala and the little wattlebird Anthochaera chrysoptera. Distinctive features of this species compared to others in the genus include a subhexagonal anterior dorsal shield on the body, a narrow genital shield, and a divided pygidial shield (the small pair of shields near the rear of the dorsum). Both of the known hosts are widespread and common in eastern Australia and it is likely that this mite is similarly ubiquitous. Studies of honeyeater phylogeny tend to place the genera Manorina and Anthochaera as close relatives, so it is possible that P. myzanthae has been infesting them since before their lineages diverged. It would be worth looking for the species in other related honeyeaters to see if we find any further clues.

REFERENCE

Domrow, R. 1964. Fourteen species of Ptilonyssus from Australian birds (Acarina, Laelapidae). Acarologia 6 (4): 595–623.