Prey and feeding phenology of the desert sand scorpion Pamroctonus mesaensis (Scorpionidae: Vaejovidae)


  • Gary A. Polis

    1. Department of Biology, University of California at Riverside
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    • *Department of Zoology, Oregon State University, Corvallis, Oregon, U.S.A.


The diet and feeding of the vaejovid scorpion Pamroctonus mesaensis Stahnke was investigated during a five-year study. Foraging and feeding behaviour are described. This scorpion is a “sit and wait” predator that eats a wide variety of cursorial, fossorial and aerial prey. Ninety-five prey species were recorded. Three year classes of scorpions exist. Each class captures a different proportion of major prey species and a significantly different average size of prey.

The proportion of each major taxon of prey in the diet is as follows: tenebrionid beetles (42%), Orthoptera (17%), other scorpions (16%) and Hymenoptera (12%). When analysed in relation to biomass, larger prey species assume more importance while smaller species are relatively less important. Although P. mesaensis ranks as the fourth most numerous prey species, they represent the most important diet item in terms of ingested biomass.

When observed, 3·75% of all scorpions were feeding. This percentage varied seasonally from a high in spring (7.0%) to a low in November and December (0.5 %). The proportions of major prey taxa in the diet also varied seasonally. Prey species were classified into three phenological categories: pulsed, seasonal and annual. Examples of each are given.