PASSALIDAE - BESS BEETLES
Paraguayan Bess Beetles range in size from 1-5.5cm (though globally they may reach 10cm in length) and exhibit social behaviours unusual amongst the Coleoptera. Some have a single short horn on the forehead, but all are elongate, with cylindrical or slightly flattened bodies and are usually black in colour. The head is narrower than the thorax and the antennae consist of 10 segments with a three to five-segmented club (usually three in Paraguayan species). The wing cases are long and elongated with longitudinal striations. Bess Beetles live under rotting logs and care for their brood, feeding larvae and assisting them in constucting their pupal case. They are capable of producing sound by rubbing the wing against the abdomen, and even larvae can produce sounds by rubbing the third leg against the coxa of the second. The members of this family are extremely similar and are best identified by careful study of their head morphology.
Click on the species names for Handbook Accounts

Relevant Resources
A key to the New World genera of Passalidae is available here in English or in Spanish.
Many thanks to Dr Jack Schuster for his assistance with information and identification of the species in this gallery.
Designed by Paul Smith 2006. This website is copyrighted by law. Material contained herewith may not be used without the prior written permission of FAUNA Paraguay. Photographs on this web-site were taken by Paul Smith, Hemme Batjes, Regis Nossent,
Alberto Esquivel, Arne Lesterhuis, Rebbeca Zarza, José Luis Cartes and Hugo del Castillo and are used with their permission.
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FIGURE 1

FIGURE 1
FIGURE 2

FIGURE 2
FIGURE 3

FIGURE 3
FIGURE 4

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FIGURE 5

FIGURE 5
FIGURE 1 - Passalus ? sp. - PROCOSARA, PN San Rafael (Paul Smith November 2007 - ECOSARA Biodiversity Database).
FIGURE 2 - Passalus punctiger - PROCOSARA, PN San Rafael (Alberto Esquivel November 2007 - ECOSARA Biodiversity Database).
FIGURE 3 - Same individual head morphology (Paul Smith December 2007 - ECOSARA Biodiversity Database).
FIGURE 4 - Paxillus leachi - PROCOSARA, PN San Rafael (Paul Smith May 2008 - ECOSARA Biodiversity Database).
FIGURE 5 - Same individual head morphology (Paul Smith May 2008 - ECOSARA Biodiversity Database).