Matthew L. Gimmel - research interests
Introduction
A reformed herper, I have a broad interest in the taxonomy and systematics of beetles and other arthropods. For my dissertation research I am focusing on a group of cucujoid beetles, the family Phalacridae or shining mold beetles. It is an extremely poorly described family, particularly in the New World. This is attributable in large part to their small size (mostly 1-4 mm in length), usually unremarkable appearance, and the apparent monotony of body form. Additionally, the most recent broad-scale treatments of the world's phalacrid fauna were those of Guillebeau (1892, 1894), which were plagued by misleading descriptions and a complete lack of illustrations. The North American species are at present almost unidentifiable despite (or because of) the grandiose efforts of Thomas L. Casey (1889-90, 1916), a figure much maligned by coleopterists for his habit of creating of a plethora of junior synonyms.
I am currently performing a revision and phylogenetic analysis of the World
genera of Phalacridae. About 635 nominal species are included in the family (World
checklist), and the number of described genera is about 50, but a
significant number of these will be synonymized. Time permitting, I also plan to revise
the entire New World fauna at the species level and finally release this
much-neglected family from the grip of taxonomic obscurity.
In addition, I am involved in the revolutionary
All Taxa Biodiversity Inventory
(ATBI) project in Great Smoky Mountains National Park, Tennessee/North
Carolina. I am investigating the faunistics and distribution of the Coleoptera of the park as part of my dissertation research. I have recently
completed a study of the Scirtidae (Marsh beetles) of the park, the results of which can be
found here.
Phalacridae -- adult morphology
Specimens of Phalacridae are common in collections and easily recognized by
their smoothly oval body outline, convex and glabrous dorsal surface (except for
a new flattened genus from Western Australia), and essentially flat
ventral surface. The pronotal margins and elytral epipleura extend sharply
ventrad, giving the appearance of a "recessed" ventral surface. A few (mostly of
the subfamily Phaenocephalinae) have slightly explanate pronotal and elytral
margins. Most are light brown to black, but many (especially tropical) species
are handsomely marked with yellow, orange, or red maculations. Additionally, a
significant proportion are endowed with brilliant structural colors, and are
dazzlingly iridescent.
The mandibles are typically short and unremarkable, but in some members of the genus Phalacrus Paykull they are elongate and contain accessory teeth which are extremely useful in species-level identification. At least one species (P. cervus Champion) has very large, asymmetric mandibles, most strongly so in the males. In all members of the family the frontoclypeal suture is lacking and the labrum is exposed. The antennae are slender and terminate in a loose 3-segmented club, though in one genus (Olibrosoma Tournier) the club appears to be 4- or 5-segmented. There is a new species of Phalacrus from Haiti whose males have greatly elongated antennae which extend beyond the apices of the elytra when swept back.
The pronotum is smooth and rounded, and broadly emarginate anteriorly to accomodate the head. The elytra range from from smooth to punctate to striate. Elytral punctures, when present, are always arranged in rows. Most genera have at least a sutural stria, and the number of striae in addition to this is often diagnostic. The procoxae range from globular (most Phalacrinae) to slightly transverse (Phaenocephalinae). They are never contiguous and are separated by a prosternal process which may be quite thin and laminate to moderately wide. The mesoventrite is quite short, and usually only visible as a thin margin at the anterior edge of the metaventral lobe. However, in the subfamily Phaenocephalinae, the medial portion of the mesoventrite protrudes ventro-anteriorly and overlaps the prosternal process when the beetle is in repose. In a few genera the mesocoxae are nearly contiguous, separated only by the small, triangular-shaped metaventral process. The metaventrite may possess a pair of lines ("mesocoxal plates," "metasternal lines," or "mesofemoral lines" auctorum) describing an area posterior to the mesocoxal cavities. These are highly useful in genus- (and often species-)level taxonomy. The metacoxae are closely approximate, and extend laterally to meet the metepisternum. The abdomen has five, usually unmodified, ventrites, but males of a new species of Phalacrus from Haiti have a row of hair tufts medially and some Stilbus have a median, serrated, posteriorly directed tooth on the posterior margin of the 3rd ventrite. The aedeagus is of the Cucujoid type, in which the tegmen forms a ring-like structure around the median lobe. The parameres are always fused medially to some extent, and these in turn may form a hinged structure with the basal piece or may be fused entirely. The tegmen often has bizarre-looking struts and other modifications that are highly diagnostic at the species level. The median lobe bears internal sac sclerites which also prove useful for species identification.
The femora are mostly broad and flattened. The tibiae are generally slender, but one species (Litotarsus tibialis Svec) has highly dilated metatibiae. The hind tibiae of the males of many species of Acylomus Sharp are modified, usually expanded apically with enlarged apical spurs. The tarsi are 4-4-4 (Phaenocephalinae) or 5-5-5 (pseudotetramerous, most Phalacrinae) or 5-5-4 (4th metatarsomere absent on leg III -- males of the Stilbus-group of genera). The relative lengths of the metatarsomeres are very important taxonomically. The tarsal claws are toothed or appendiculate.
Phalacridae -- life history
Life histories are generally poorly known for the group, except for a few
European and North American species. These are reviewed by Steiner (1984). Most are associated with fungi, with a few
notable exceptions. Adults of the genera Olibrus, Tolyphus, Merobrachys,
Litochrus (sensu stricto), and Parasemus are most frequently
collected from flower heads of members of the family Asteraceae. They are
probably palynophagous. Larvae of Olibrus develop one per flower head,
hollowing out a receptacle as they grow and apparently do not ingest solid plant
tissue, but receive nutrition from the sap of the plant. The only known specimens of a new genus were collected
as adults from the male cones of Macrozamia (Cycadales:
Zamiaceae) in Western Australia, and also are probably feeding on pollen.
All members of the genus Phalacrus whose habits are known feed either on smut fungi (Basidiomycota: Ustilaginomycetes) or rust fungi (Basidiomycota: Pucciniales). In Europe, the larvae and adults of P. corruscus (Panzer) feed on spores of smuts of the genera Ustilago and Tilletia on wheat, oats, and barley. P. grossus Erichson larvae and adults feed on Ustilago striaeformis (Westend.) V. Neissl., which occurs on rye. P. substriatus Gyllenhal breeds in Cintractia, which occurs on sedges of the genus Carex. An Indian species, P. immarginatus Champion, develops in Sporisorium scitamineum (Syd.) M. Piepenbr., M. Stoll & Oberw., a sugarcane smut. The North American species P. politus Melsheimer breeds in Ustilago maydis (DC.) Cda. (corn smut) and smuts occurring on the grass Panicum dichotomiflorum Michx. Adults and larvae of Phalacrus uniformis (Blackburn), which occurs in Australia and has been introduced into New Zealand (where it is the only phalacrid occurring there), feeds in the galls of the rust fungi Uromycladium notabile (Ludwig) McAlpine and U. acaciae (Cooke) Sydow, which infect Acacia mearnsii DeWildemann. Larvae of the monotypic genus Phalacropsis (for P. dispar (LeConte)), which is closely related to (and may actually belong in) the genus Phalacrus, feed on the aecia of Peridermium spp. (pine stem rust) on several species of Pinus.
Species of the genus Acylomus, probably the largest and most widespread genus in the New World, inhabit dead vegetation, especially hanging dead-leaf clusters, grass stalks, and legume pods. The adults and larvae are known to feed on saprobic surface molds growing on the drying plant material. Acylomus pugetanus Casey, by contrast, is known only to feed in the sclerotia of Claviceps spp. (Ascomycota: Clavicipitaceae), the causative agent of ergot, which occurs on the seed heads of many species of grasses (Poaceae).
A member of the genus Litochropus Casey, L. clavicornis Casey, occurs in the fruiting bodies of Daldinia spp. (Ascomycota: Xylariaceae), a common wood-decaying fungus. Larvae apparently feed on the sterile inner tissue, while the adults consume mainly spores.
LITERATURE CITED
Casey, Thomas Lincoln. 1889–1890. Coleopterological Notices I. Annals of the New York Academy of Sciences, 5: 39–198.
Casey, Thomas Lincoln. 1916. Phalacridae. Memoirs on the Coleoptera, 7: 35–86.
Guillebeau, Francisque. 1892. Revision des Phalacrides de la fauna paléarctique. Revue d’Entomologie, 11: 141–197.
Guillebeau, Francisque. 1894. Descriptions de quelques espéces de la famille de Phalacridae de la collection de M. Antoine Grouvelle. Annales de la Société Entomologique de France, 63: 275–310.
Steiner, Warren E., Jr. 1984. A review of the biology of phalacrid beetles (Coleoptera). Pp. 424–445. In: Wheeler, Quentin and Meredith Blackwell (eds.). Fungus-Insect Relationships: Perspectives in Ecology and Evolution. New York: Columbia University Press. 514 pp.