The biology and ecology of the cosmopolitan weevil P. spadix has been studied in the UK. The weevil inhabits timber in the mid to high intertidal zones where it withstands submersion in seawater for up to 6hrs with each tide. In the laboratory, adult mortality following submersion in still distilled water, still seawater, pressured and aerated seawater showed P. spadix to survived these conditions for up to 100hrs in still seawater and more than 144hrs in aerated seawater which mostly resembles the marine intertidal zone. The mean adult recovery times following 100 hrs submersion in still seawater averaged 6hrs , whilst following 118 hrs submersion in aerated seawater the mean recovery time was 1 hr, indicating that adults use the air supply in the water. These results differed significantly from those obtained for adult Euophryum confine Broun, a terrestrial wood-boring weevil (Col. Curc. Cossoninae.). In still seawater 100% mortality was reached following 6hrs of submersion. In addition, details of adult P. spadix respiratory morphology were examined using scanning electron microscopy. P. spadix is wingless and the elytra are immovably joined along the midline. The sub elytral cavity thus formed underneath the elytra bears setae patterns on the dorsal abdomen and underside of the elyrta suffuciently dense to trap air. In the winged E. confine adults, these structures were not present. In comparison the spiracles in P. spadix open into the sub elytral cavity, whilst in with E. confine spiracles are positioned more towards the pleura and smaller in opening. These differences strongly suggest specialised marine adaptations in adult P. spadix.
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA