''Pachyrhynchus'' is a genus of

weevil Weevils are beetles belonging to the superfamily Curculionoidea, known for their elongated snouts. They are usually small – less than in length – and herbivorous. Approximately 97,000 species of weevils are known. They belong to several fa ...

s in the family

Curculionidae The Curculionidae are a family of weevils, commonly called snout beetles or true weevils. They are one of the largest animal families with 6,800 genera and 83,000 species described worldwide. They are the sister group to the family Brentidae. Th ...

. Most species are found on Southeast Asian islands.

Description

''Pachyrhynchus'' have

aposematic Aposematism is the Advertising in biology, advertising by an animal, whether terrestrial or marine, to potential predation, predators that it is not worth attacking or eating. This unprofitability may consist of any defenses which make the pr ...

coloration. They are flightless, with completely fused

elytra An elytron (; ; : elytra, ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometime ...

. The eggs are inserted into plant tissues. The larvae will then develop and feed inside the stems of the host plants. The pattern of diversification in this genus suggests stepping-stone dispersal. It is hypothesized that these flightless insects disperse from one island to another by rafting on their host plants. This could be facilitated by the wood-boring life-style of the eggs and larvae, as well as the air cavity under the fused elytra that help adults to float. However, experiments with ''Pachyrhynchus jitanasaius'' suggest that survival of adults in water—fresh, brackish, or marine—is low (most died within 12 hours, and no individual survived longer than 40 hours). On the other hand, the larvae living in ''

Barringtonia asiatica ''Barringtonia asiatica'', known variously as fish poison tree, putat and beach Barrintonia among other names, is a species of plants in the brazil nut family Lecythidaceae. It is native to coastal habitats from Tanzania and Madagascar in the ...

'' fruit is higher, with a fraction of larvae surviving six days of sea water exposure and successfully emerging as adults. This suggests that the eggs and larvae are the primary dispersive stages in ''Pachyrhynchus''. The coloration of the scales in multiple species is produced structurally, by means of

photonic crystals A photonic crystal is an optical nanostructure in which the refractive index changes periodically. This affects the propagation of light in the same way that the structure of natural crystals gives rise to X-ray diffraction and that the atomic ...

(more strictly known as photonic band-gap materials within the biophysics literature); this has been the focus of multiple studies. Other research has shown that the eggs can survive digestion in certain birds, such as '' Hypsipetes leucocephalus'' and '' Turdus chrysolaus'', which may be another explanation for the genus' successful dispersal.

Species

Species include:

References

Catalogue of Life

Barry.fotopage.ru

Wtaxa
{{Taxonbar, from=Q3360154 Entiminae Curculionidae genera Taxa named by Gustaf Johan Billberg