''Pachyrhynchus'' is a genus of
weevil
Weevils are beetles belonging to the Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...
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.
T ...
. Most species are found on Southeast Asian islands.
Description
''Pachyrhynchus'' have
aposematic
Aposematism is the advertising by an animal to potential predators that it is not worth attacking or eating. This unprofitability may consist of any defences which make the prey difficult to kill and eat, such as toxicity, venom, foul taste or ...
coloration. They are flightless, with completely fused
elytra
An elytron (; ; , ) 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 (sometimes alterna ...
. 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'' (fish poison tree, putat or sea poison tree) is a species of ''Barringtonia'' native to mangrove habitats from islands of the Indian Ocean in the west to tropical Asia and islands of the western Pacific Ocean. It is g ...
'' 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''.
Species
Species include:
References
Catalogue of LifeBarry.fotopage.ruWtaxa
{{Taxonbar, from=Q3360154
Entiminae
Curculionidae genera
Taxa named by Gustaf Johan Billberg