Natural history observations of Utabaenetes tanneri (Orthoptera: Rhapidophoridae), a Colorado Plateau endemic sand treader

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Tim Graham, independent, Moab, UT

Background/Question/Methods
Sand treaders are camel crickets (Orthoptera: Rhaphidophoridae) with adaptations for living in sandy habitats. Four genera of sand treaders are found in North America. Utabaenetes tanneri is a sand treader endemic to south-central Utah. Little is known about this species, including its complete range. It occupies active sand dunes with little vegetation. It has morphological and behavioral characteristics that are unusual among camel crickets and even among the sand treaders, such as a crepuscular-diurnal activity, coloration, and mating behavior. The goal of this work is to learn more about the natural history of U. tanneri and compare and contrast its ecology with what is known of the ecology of another other large sand treader in Utah, Daihinibaenetes giganteus (Weissmann 1997). Ad hoc observations were made March through June over the past 13 years, in spring during the last nymphal instar and adult stages of the life cycle. Most data are from field observations but I have had some captive sand treaders for a few weeks kept in a large terrarium outside. Food habits, activity patterns, burrow characteristics and mating behaviors were recorded.
Results/Conclusions
Utabaenetes tanneri are omnivores; over 25 different food items were observed being carried and/or consumed including live and dead plant parts, fungus, fecal pellets, and insects. Plant fragments and other potential food items (e.g., rabbit pellets) were often seen in burrows and U. tanneri was frequently observed carrying plant parts into burrows. This is consistent with observations of other sand treaders including D. giganteus (Weissman 1997). Nymphs of U. tanneri are tan and primarily nocturnal. Mature U. tanneri are shiny black after their last molt and become active on the surface at sunrise, remaining active until mid-morning; all other sand treaders are tan lives and primarily nocturnal their entire lives. Burrows varied in depth and trajectory and were relatively simple. I didn’t find any branching or complex burrows as reported for D. giganteus (Weissmann 1997). Only three were occupied by more than one individual; two with a single pair (one male and one female), the third burrow had one male and four females. Unlike D. giganteus, U. tanneri mate mostly on the surface during morning hours. Males will antennate any cricket they encounter then turn around and back up to potential mates. There are many aspects of U. tanneri ecology yet to explore, such as how does a large black insect survive on bare sand during the day?