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'Pachyrhynchus smaragdinus
Brentidae - Pachyrhynchus smaragdinus.jpg
Museum specimen of Pachyrhynchus smaragdinus
Scientific classification

Billberg, 1820

Pachyrhynchus is a genus of weevils in the family Curculionidae. Most species are found on Southeast Asian islands.[1]


Pachyrhynchus have aposematic coloration. They are flightless, with completely fused elytra. The eggs are inserted into plant tissues. The larvae will then develop and feed inside the stems of the host plants.[2]

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.[1] 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 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.[1][3]


Species include:


  1. ^ a b c Yeh, Hui-Ying; Tseng, Hui-Yun; Lin, Chung-Ping; Liao, Chen-Pan; Hsu, Jung-Ya & Huang, Wen-San (2018). "Rafting on floating fruit is effective for oceanic dispersal of flightless weevils". Journal of Experimental Biology: jeb.190488. doi:10.1242/jeb.190488. PMID 30352828.
  2. ^ Tseng, Hui-Yun; Huang, Wen-San; Jeng, Ming-Luen; Villanueva, Reagan Joseph T.; Nuñeza, Olga M. & Lin, Chung-Ping (2018) [2017]. "Complex inter-island colonization and peripatric founder speciation promote diversification of flightless Pachyrhynchus weevils in the Taiwan-Luzon volcanic belt". Journal of Biogeography. 45 (1): 89–100. doi:10.1111/jbi.13110.
  3. ^ "How flightless beetles wander the Pacific". The Economist. 2018-11-01. Retrieved 28 November 2018.