Tenebrionidae - Eleodes longicollis
Size: 29 mm
Group Guild Status
Trogloxene Scavenger Uncommon
A variety of tenebrionid beetle species in the southwestern U.S. are associated with small burrowing mammals, where they forage among nesting materials and/or feed on waste of the host animals. It should come as no surprise then that many of these beetles are also occasionally found in caves, where the mammals they associate with also often make their homes. The presence of tenebrionid beetles, including species of Eleodes, is not unusual in caves, and a few Eleodes (subgenus Caverneleodes) are cave-adapted to various degrees (Triplehorn 1975). We have at least one cave-adapted troglophilic tenebrionid beetle in Arizona (Eschatomoxys pholeter), which occurs in a few caves in Grand Canyon National Park (Pape et al. 2007; 2014).
We have so far observed four species of tenebrionid beetles in the cave, but none of these are common, and we have a total of only eight observations of all four species combined. None of these species appear to have any morphological adaptations for living in caves, and we consider them all to be trogloxenes. All but one of the records of these species were near cave entrance areas (Crinoid and LEM Rooms and the Jackrabbit Shaft and Gallery). E. longicollis is known to be associated with harvester ants, where the beetles scavenge off the organic matter deposited at the periphery of the ant nest (Slobodchikoff 1979). E. longicollis may be the most common tenebrionid species in the cave, and has been observed on four occasions, twice in the Crinoid Room, once in the LEM Room (Photo 1), and the single deep penetration of the cave in the far north end of the Big Room. This latter observation was at night on September 28, 2009, where we found the animal walking the tour trail. It had likely come all the way from the cave entrance area. This was during the fall closure time of the Big Room. The initial study (Welbourn 1999) recorded a species of Eleodes from the “entrance area” of the cave, but did not specify whether this was in the breakdown rubble in the open Entrance Sink, in the first room (Crinoid Room), or elsewhere in the front part of the cave. We do not know if the original observation represents this species, but this seems probable.
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