Ptiliidae Heer, 1843

Berx, Peter, Bosmans, Bart, Dekoninck, Wouter, Janssen, Marc, Stassen, Eugène & Crevecoeur, Luc, 2023, Faunistic survey of myrmecophilous and other ant-associated beetles and spiders in the Belgian province of Limburg (Araneae, Coleoptera, Hymenoptera: Formicidae), Belgian Journal of Entomology 141, pp. 1-61 : 26

Ptiliidae Heer, 1843

In the family Ptiliidae we are dealing with the smallest of all coleopterans. Some species are just 300 μm and the measurements of the specimens we collected during this long-term survey (Annex) fall within the following averages: 580–630 μm ( Micridium halidaii ), 1050–1180 μm ( Ptenidium laevigatum ), 750–850 μm ( Pteryx suturalis ) ( Fig. 21B ) and 600 – 650 μm ( Ptilium myrmecophilum ) ( Fig. 21C ) ( FREUDE et al., 1971) The minute size of these beetles and the difficulty of identification, contribute to the poor study of this group. It is therefore hardly surprising that little is known about the biological connection between these inconspicuous beetles and the ants, and that there are only sporadic reports of observations in or near an ants’ nest.

The observation of Micridium halidaii , associated with the ants L. brunneus and L. niger (or L. platythorax ) (Annex) on 16 June in 2008 is the first mention of this species in Belgium and even in the Benelux. The specimen was collected in the Kolmont forest reserve in Tongeren by wrapping a glue ring around the trunk of a dead beech tree, on which, however, no ant was found.

Figures

Fig.21. A, Acrotrichis intermedia (Gillmeister, 1845) (range 1.0-1.1mm). B, Pteryx suturalis (Heer, 1841) (range 0.75-0.85mm). C, Ptilium myrmecophilum (Alibert, 1844) (range 0.6-0.65mm). © U. Schmidt.