The huhu beetle (Prionoplus reticularis) is a longhorn beetle endemic to New Zealand. It is a large, visually distinctive species whose adults reach up to five cm (2 in) in length. It is widespread throughout New Zealand, occurring up to 1,400 m (4,600 ft) in altitude. Although it is unable to eat as an adult, the larva feeds and burrows in the dead wood of trees, almost entirely feeding on gymnosperms such as rimu and Monterey pine. As a larva, it can grow to sizes of 50–70 mm (2.0–2.8 in) and has a cylindrical appearance with a creamy colour. During this stage, which is high in protein and fat, it is edible and has been described as tasting similar to peanut butter. It has a history of consumption by the Māori, with the larva being consumed either raw or traditionally cooked in a hāngī. The adult lives for roughly two weeks. It is nocturnal and is strongly attracted to light, such as that produced by human habitation. The female appears to produce olfactory cues to attract the male. During its larval stage, the beetle can potentially take one to two years to reach maturity, although this has been achieved more quickly in laboratory conditions. The intestinal tract of the larva hosts a diverse range of microorganisms that may assist in digestion of wood. Because the larva burrows into logs, New Zealand has to treat logs before exporting them to prevent the beetle spreading to other countries. This is done by fumigating or heating the logs, which is done by government-approved third parties. Many predators such as native birds and introduced mammals are known to prey upon the beetle. Prionaphes depressus, a species of fairy wasp exclusively parasitises the beetle's eggs. It was first described in taxonomic literature in 1843 by Scottish zoologist Adam White from a specimen collected in the Bay of Islands.
Taxonomy The first specimen of huhu beetle to be used for taxonomic purposes was collected by British botanist Andrew Sinclair during a voyage in which he visited the Bay of Islands and went on expeditions alongside British botanists William Colenso and Joseph Dalton Hooker. The specimens he collected from this trip were donated to the British Museum (now Natural History Museum of London). From the material Sinclair collected, Scottish zoologist Adam White formally described the species in 1843. The type specimen (the specimen on which the species description is based) is stored in the Natural History Museum of London. The huhu beetle larva and pupa, the juvenile and pre-adult life stages, were later described by New Zealand entomologist Thomas Broun in 1880 and a brief description of their typical habits were given from samples collected from Parua Bay near Whangārei. Broun then produced a revised description of the species in his landmark Manual of the New Zealand Coleoptera publication in the same year.
Phylogeny
A 2023 study examined the phylogeny (evolutionary history) of Australian Rhipidocerini using genomic data produced by shotgun sequencing. The study placed Prionoplus in the Rhipidocerini, a tribe within the longhorn beetles, and positioned it as basal to all other Rhipidocerini species that were sequenced (all of which were Australian species), meaning it split off earlier than the other species that were studied.
Etymology The Māori name huhu is ultimately Austronesian in origin from the root form *bukbuk. Cognates, words in different languages derived from a common ancestor, in the more closely related Malayo-Polynesian languages (like Tagalog bukbok) refer to weevils that infest wood and rice across tropical Southeast Asia. In Māori, huhu has semantically evolved to also refer to its larval form (also tunga haere, tunga rākau). As the larva reaches maturity, it ceases to bore in wood and sheds its skin. This stage is known in Māori as tātaka. It then develops wings and legs, and while it is still white, it is known as pepe or pepe te muimui. Finally, it emerges and flies off to reproduce in its adult stage and is known as tunga rere.
Description
Adult The adult huhu beetle is unmistakable and easily identified by its large size (reaching around five cm [2 in] in length) and distinctive appearance. Overall, the whole body of the adult is a dark brown colour. The head and thorax have a thick layer of brown hair-like setae giving it a fuzzy appearance. As is typical of longhorn beetles, the antennae are long, extending around three quarters of the beetle's length. The mandibles are large and curved with a sharp end. Spines are present on the femur and tibia, the third and fourth segments of the legs. The elytra (hardened plates that cover the abdomen) are brown and have three pale yellow veins running down the length of the elytra with numerous cross veins forming a reticulated pattern. The male antennae are longer than the female's and also possess some sensilla (microscopic sensory organs) that are not present in female antennae. There is a single record of a female developing an extra pair of ovaries.
Pupa The pupa is 35–40 mm (1.4–1.6 in) in length. The head and the pronotum (the main segment of the thorax), are covered in scattered setae, with the pronotum also having a small protuberance at its sides. The mesonotum and metanotum, the second and third segments of the thorax respectively, both have protuberances too, with the former having them in the middle of the segment's end, and the latter having them at the beginning of the segment. The first to eighth segments of the abdomen are covered in short hairs on the upper surface that gradually become more sparse in each consecutive segment. At the end of the abdomen there are two cone-shaped horns that are darkened at their tips.
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