BYRRHIDAE Latreille, 1804 Birrhii Latreille, 1825; Brachymera Thomson, 1859; Byrrhida Meixner, 1935; Syncalyptidae Moursy, 1961   PILL or MOSS BEETLES

Recognition: For Costa Rican species, the very small size (<1.2 mm), convex and compact shape, deflexed head, transverse front coxae, retractile appendages, erect dorsal bristles, and moss and alga associated habit are distinctive of this family.

Habitus: Body form oval to elongate oval, strongly convex, length approximately 1.0-1.2 mm. Integument with erect clavate bristles. Color variable, usually of gray, brown or black, often with an encrustation of sand or mud. Head hypognathous, frons convex, narrower than prothorax. Eyes slightly emarginate, situated on sides of head; hidden when head retracted into prothorax. Clypeus strongly reduced. Labrum freely articulating, shallowly emarginate. Antenna 11-segmented, clavate-capitate. Mandibles with apical teeth, a deep notch at middle, a blade-like molar area, and a basal brush of setae. Maxillary palpus 3-segmented, labial palpus 2-segmented, terminal segment pear-shaped. Thorax compact, prothorax tightly fitting agains mesothorax. Pronotum convex, lateral margin finely carinate, posterior margin smooth. Hypomeron large, subtriangular, with cural depressions. Prosternum V-shaped on disc, relatively broad between coxae, intercoxal process received into a deep cavity on mesosternum; anterior coxal cavities broadly open behind. Scutellum minute, subtriangular. Elytra entire, strongly convex, surface finely punctate, striae obsolescent, epipleural fold extending to end of elytron, venter near apex with narrow laminar flange. Mesosternum short, broad in front, narrow behind. Metathorax alate. Wing nearly veinless, apical field long, subequal in length to veined basal portion; radial cell short, oblique; medial area veins reduced, wedge cell absent. Metasternum much broader and longer than pro- and mesosternum, with a median longitudinal suture, transverse suture lacking. Legs with anterior coxae transverse, separate; middle coxae globular, slightly transverse, separate; hind coxae transverse, approximate medially, nearly attaining the elytral epipleura laterally; trochanters triangular, large; femora somewhat flattened; tibiae slender or stout, flattened and expanded apically, densely covered with setae or spines; tarsal formula 4-4-4 (normally 5-5-5 in family), tarsomeres increasingly larger from first to 3rd, 4th absent, 5th long, claws simple. Abdomen with 5 ventrites; ventrites 1-2 connate. Male genitalia with median lobe with apex acute, parameres lacking; pars basalis subcylindrical. Female genitalia with gonocoxites large; styli subapical, short; baculi absent.

Larvae (unknown for C.R. species) elateriform; mature length 2-3 mm; terga with rows of setae. Head exserted, hypognathous, with lyriform epicranial suture surrounding frons; stemmata 6 each side; antennae short, three-segmented; clypeus separate from frons, transverse; labrum freely articulating; mandibles symmetrical, single to multidentate, robust, with a large brush of setae at the base of the cutting edge, mola absent; maxilla with palpiform galea, 1-2 segmented; lacinia falciform or truncate, with spiniform mesal margin, palpus 4-segmented; cardo bipartite, fused stipes, setiferous. Labium with ligula, palpus 2-segmented. Thorax with the pronotum as long as the meso- and metathorax combined, legs short, 5-segmented, with bisetose tarsungulus. Abdomen 10-segmented; 8th segment often transversely carinate, or operculate; 10th segment short, rarely with strong ventral hooks; urogomphi absent. Spiracles biforous, present on mesothorax and abdominal segments 1-8, closing apparatus absent.

Ecology:  Most byrrhid species are obligate moss and liverwort feeders as both adults and larvae, though feeding on lichens, algae, leaves and stems of succulent herbs, and grass roots by a few specialized species is recorded.  Adults of all bryophagous taxa are surface grazers on host mosses.  Larvae of most species are bryophagous and burrow through gametophyte layers, and underlying friable substrates.  The Costa Rican species is probably associated with thin layers of moss protonemata and algae on silty shores and banks, and could be found active on their hosts.  Adults retract their legs and antennae into ventral recesses and becomes motionless when disturbed.  The Costa Rican species can be found with light traps, flight intercept traps, and searching appropriate microhabitats.

Status of the Classification: El Moursy (1961) suggested that Syncalyptinae should be regarded as a separate family, Syncalyptidae. However, all subsequent authors have retained the subfamily status of this group. The neotropical taxa are poorly studied, but all known forms from Central America are attributable to Chaetophora.

Diversity and Distribution: There are about 290 species of byrrhid known globally. Only one undescribed species of Chaetophora is presently known from Costa Rica.
 
 
 
 

CLASSIFICATION OF COSTA RICAN BYRRHIDAE
 
 

Genus: Chaetophora Kirby and Spence, 1823

Syncalypta Stephens, 1830

Provincial Records: Alajuela, Puntarenas

General Distribution: northern Costa Rica

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BIBLIOGRAPHY
 

DALLA TORRE, K.W. VON 1911. Fam. Byrrhidae. Coleopt. Cat. 14(33): 12-33.

EL MOURSY, A.A. 1961. A tentative classification of and a key to the North American genera of the family Byrrhidae (new sense)
        and family Syncalyptidae (new status) (Coleoptera, Polyphaga, Byrrhoidea). Coleopts. Bull. 15: 9-15.

JOHNSON, P.J. 1990. Notes on the naturalization of two European Byrrhidae (Coleoptera) in North America.  J. New York Entomol. Soc.,
        98: 434-440.

JOHNSON, P.J. 1991a. Taxonomic notes, new records, and a key to the adults of North American Byrrhidae (Coleoptera).  Proc. Entomol.
        Soc. Wash., 93: 322-332.

LAWRENCE, J.F. 1981. Coleoptera, pp. 482-553. In Parker, S.P. (ed.), Synopsis & Classification of Living Organisms, vol. 2.  McGraw-Hill
        Book Co., New York.

LAWRENCE, J.F. 1991. Byrrhidae, pp. 384-386. In Stehr, F.W. (ed.), Immature Insects, vol. 2. Kendall/Hunt Publ. Co., Dubuque.
 
 

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