Discolomatid beetles, Discolomid beetles, Mexican hat beetlesFloyd W. Shockley and Andrew R. Cline
- Aphanocephalinae Grouvelle 1912
- Aphanocephalus Wollaston 1873
- Fallia Sharp 1902
- Parafallia Arrow 1887
- Profallia John 1954
- Solitarius John 1943
- Discolomatinae Horn 1878
- Discoloma Erichson 1848
- Cassidoloma Kolbe 1897
- Notiophyginae Jacobson 1915
- Dystheamon Grouvelle 1927
- Holophygus Sharp 1887
- Parmaschema Heller 1912
- Notiophygus Gory 1834
- Pachyplacus John 1935
- Praviclava John 1941
- Pondonatinae John 1954
- Katoporus John 1956
- Pondonatus John 1954
- Cephalophaninae John 1954
- Cephalophanus John 1940
Discolomatidae is a family of small to moderately-sized (2-4 mm) beetles whose members have generally been considered mycophagous or saprophagous, although little is known about their specific biology. The family includes 16 genera and ~400 species arranged within 5 subfamilies: Aphanocephalinae, Cephalophaninae, Discolomatinae, Notiophyginae and Pondonatinae. Discolomatids are distributed throughout the tropical and subtropical regions of the world, with greatest diversity in the Afrotropics and southeastern Asia.
Adults and larvae are most often collected from under bark (Lawrence 1982, Cline and Gillogly pers. obs.). However, Parafallia and Holophygus have also been recovered from leaf litter (Cline and Ślipiński in press), Aphanocephalus and Fallia have been collected feeding on the surface of fungi, and Notiophygus and Discoloma species have been recorded from lichens (Lawrence 1991, Cline & Ślipiński in press).
Within Discolomatidae, several instances of myrmecophily are known. Cline and Ślipiński (in press) reviewed these associations and discussed some of the morphological adaptations in discolomatids likely exhibited by ant inquilines. At least 3 genera have been recorded in association with ants (Notiophygus, Katoporus and Holophygus). Cassidoloma has also been collected in association with ants (Shockley and Robertson pers. comm.). In addition, several other taxa (e.g., Aphanocephalus, Parafallia) possess features which suggest they may also be myrmecophiles; however, no specific associations have been reported.
- Oval to almost circular habitus, typically dorsoventrally flattened to some degree
- Antennae 9 or 10-segmented (8-segmented in Fallia) with a 1-segmented apical club
- Palpomere II of maxillary and labial palpi swollen
- Prothorax with 2 conspicuous tubular gland openings near front and hind angles
- Lateral margins of elytra often broadly explanate, bearing 6 or more tubular gland openings
- Coxae on all legs appear globular and widely separated, but actually transverse and partially internalized, visible coxal cavities small and round
- Tarsi 3-3-3 in both sexes, all tarsomeres and claws simple
- Often wingless
Larvae for this group are poorly known, but described forms are quite distinct from other cucujoid larvae. Discolomatid larvae can be distinguished from other similar larvae by the following combination of characters (based on Lawrence 1991, Lawrence et al. 1999b, Cline & Ślipiński in press):
- Body strongly onisciform and flattened
- Dorsum highly sculptured, tuberculate, or granulate
- Head concealed by pronotum, with epicranial stem short or absent, frontal sutures sinuate
- 3 pairs of stemmata
- Antennae long, 2-segmented (segment III absent), sensory appendage moderately long
- Mandibles with aspirate well-developed mola, bearing a broad hyaline prostheca
- Maxillary and labial palpi 2-segmented
- Legs well-developed, 5-segmented with unisetose tarsungulus
- Urogomphi absent
Crowson (1955) placed Discolomatidae (as Discolomidae) within the Cerylonid Series (CS) of Cucujoidea. From a morphological standpoint and compared to other CS families, Discolomatidae seems the most likely to form a natural group, based on several unique synapomorphies (listed above) that unite its constituent taxa. However, discolomatids as a group have been variably classified within many other families including Cerylonidae, Coccinellidae, Colydiidae, Corylophidae, Latridiidae, Nitidulidae and Trogossitidae (see Cline & Ślipiński in press for specific references). Previous cucujoid workers (Lawrence 1991, Ślipiński 1990) have proposed a possible relationship between Cerylonidae (subfamily Murmidiinae) and Discolomatidae based on several morphological features which may be potential synapomorphies uniting the two groups.
Despite the inclusion of discolomatids in several recent phylogenetic studies, there have been no specific attempts to resolve internal relationships of the family. However, these studies have yielded interesting hypotheses of sister group relationships between Discolomatidae and the remaining CS families. Ślipiński & Pakaluk (1991) recovered Discolomatidae in an unresolved polytomy with Cerylonidae (excluding Euxestinae), and three endomychid subfamilies (Anamorphinae, Eupsilobiinae and Merophysiinae) based on two characters (closed mesocoxal cavities and 5 abdominal spiracles) mapped onto an intuitive phylogeny of relationships between the CS families.
The first formal phylogenetic analysis to include Discolomatidae was that of Hunt et al. (2007) using Bayesian analysis of 3 genes (16S, 18S and COI). In that study, Discolomatidae was recovered as monophyletic but nested within the family Cerylonidae. Robertson et al. (2008) also recovered Discolomatidae as monophyletic but sister to Cerylonidae using Bayesian analysis of 2 genes (18S, 28S). Interestingly, parsimony analyses in that study consistently recovered Discolomatidae as sister to a clade comprising Anamorphinae+Corylophidae. Ślipiński et al. (2009), using maximum parsimony analysis of adult and larval morphological characters, recovered a monophyletic Discolomatidae with variable sister group associations. Discolomatidae was recovered as sister to a clade comprising Endomychidae+Coccinellidae based on adult characters alone, however the inclusion of larval characters resulted in Discolomatidae being recovered in an unresolved polytomy with Endomychidae, Coccinellidae and Corylophidae. At present, sister group affinities of Discolomatidae remain far from resolved.
- Vernacular Names: Discolomatid beetles, Discolomid beetles, Mexican hat beetles
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Ślipiński, A., W. Tomaszewska and J.F. Lawrence. 2009. Phylogeny and classification of Corylophidae (Coleoptera: Cucujoidea) with descriptions of new genera and larvae. Systematic Entomology 34: 409-433.
Floyd W. Shockley
Dept. of Entomology, National Museum of Natural History, Smithsonian Institution
Correspondence regarding this page should be directed to Floyd W. Shockley at and Andrew R. Cline at
Page copyright © 2011 Floyd W. Shockley and
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- First online 21 September 2009
- Content changed 21 September 2009
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Shockley, Floyd W. and Andrew R. Cline. 2009. Discolomatidae http://tolweb.org/Discolomatidae/9168/2009.09.21 in The Tree of Life Web Project, http://tolweb.org/. Discolomatid beetles, Discolomid beetles, Mexican hat beetles. Version 21 September 2009.