A REVIEW OF THE DISTRIBUTION AND BIOLOGY OF THE SMALL CARRION BEETLE PRIONOCHAETA OPA CA OF NORTH AMERICA (COLEOPTERA; LEIODIDAE; CATOPINAE)*

the the a on the systematics, biology, and evolution of the catopine

Diagnostic Description. From most other small beetles commonly occurring at carrion or other decomposing matter, the Catopinae can be distinguished by their antennae, having a five segmented club with segment 8 smaller than segments 7 and 9. P. opaca is easily separated from all other American catopines by the following combination of characters: It is the largest catopine in eastern North America (ranging from 4 to 5.5 mm in length in a normally reflexed condition). The pronotum and elytra have neither striae nor a coarsely granular surface, but are covered with abundant setae with prominent basal sockets. Males have expanded front tarsal segments but the first tarsal segment of the middle leg of males is not enlarged or swollen (a character of the tribe Catopini). The elytra appear to have a pale blue-grey pru-*Manuscript received by the editor December 22, 1977 299 300 Psyche [September-December inose surface when viewed with a strong light at a low angle (caused by diffraction of light on the finely striate surface of small scales) but otherwise the species is of a reddish-to-dark brown color. The most distinctive character is the very long spur on the hind tibia. The spur is longer than the first metatarsal segment and has distinctly serrated fringes on two margins. Other descriptive and taxonomic details can be found in Horn (1880), Hatch (1930), Jeannel (1936), and Szymczakowski (1964), and in figures 1-7.
Variation. Except for differing body sizes, no morphological variation is evident in specimens from throughout the range of the species. On the male genitalia, differing degrees of sclerotization of the paramere tips causes them to twist to differing amounts when dried. The setae on the internal face and ventral margin of the paramere tips (not drawn in figs. 6, 7) do not vary.
Geographic distribution. The species has a wide distribution over most of the region covered by the deciduous broad-leaf forest of temperate eastern North America ( fig. 8 (Quebec City). These collections contain about 400 specimens. My own collection included 1200 specimens. Many of these are now deposited in the MCZ, Field Museum, and Canadian National Collection. Literature records of Blatchley (1910), Brimley (1938), Leonard (1926) and Kirk (1969) have also been used on the map because they are probably correct in reporting on this distinctive species. The imprecise record for "southwestern Arkansas" of Hatch (1933) and the doubtful record of Jeannel (1936) for Breckinridge, Colorado, have not been used.
The forest population near Marianna in Jackson county in northern Florida is probably disjunct and relictual. The Marianna lowlands is known as a floristic relict area (Mitchell, 1963) Jeannel, 1936. similar situation is suggested for many arthropods (personal data).
The species probably does not occur in peninsular Florida because extensive trapping there by Dr. Alfred Newton and myself has failed to find it. Another disjunct population is in the forested Black Hills of western South Dakota. This population is separated from the rest of the species' range to the east by the grasslands of the Great Plains. The beetle undoubtedly reached the Black Hills when the intervening country was more forested (with at least more extensive streamside gallery forests) during a cooler and more moist glacial period. It has become isolated with the expansion of the prairies in the warmer and drier climate of the present interglacial.
Habitat preferences and feeding biology. Most specimen records show that the preferred habitat of the species is in moist and 302 Psyche . Map of distribution of Prionochaeta opaca Say. Closed dots, epigean records. Open dots, cave records. A dot may indicate more than one county locality record. Disjunct forest populations occur in the Black Hills of South Dakota, and in northern Florida. These and the prevalence of cave records in the south indicate adjustment of the species' range to post-glacial climatic conditions. forested situations. Experimental field studies back this up. Walker (1957) took P. opaca during systematic trapping in Tennessee only in mesic and bottom forest, and not in drier ridge forest and old field habitats. Reed (1958) found the species in Tennessee on carrion in forests but never in pastures. Within a single mesic forest there is probably little microhabitat preference. Pirone (1974), in a trapping study in New York, collected about equal numbers of beetles in both forested slope and level sites. Shubeck (1969) found the species to be more common in a shrub community of arrowwood and greenbrier than in maple-leaved viburnum and black-haw shrub areas, in a New Jersey oak-hickory climax forest.
Wherever the beetle has been collected it seems to be a generalized scavenger on decaying organic matter, perhaps actually feed-1977] Peck Small Carrion Beetle 303 ing on the fungi or bacteria associated with decomposition. It has been taken on carrion throughout its range and can be easily trapped with carrion baits (see above, and Newton and Peck, 1975). Shubeck (1969) noticed that P. opaca increased in numbers as other carrion beetles decreased, at a later stage of succession of the carrion fauna, when the carcass was drying out. In contrast, Johnson (1975) found the species in an Illinois forest to be most common in the decay stage of decomposition. I have commonly taken P. opaca throughout its range in traps baited with human dung, and have found it on fox dung in Iowa. It occurs often in animal burrows and dens where it is probably a scavenger on nest or waste materials. So far, it have been recorded in literature and on specimen labels in woodchuck burrows in Indiana, New York, and Pennsylvania; in a fox hole in Massachusetts; in rabbit nests in Indiana; in a belted kingfisher nest in New York; and in a buzzard nest in Maryland. It has been taken by Berlese-Tulgren funnel processing of decaying plant debris from Florida to New York and Wisconsin, and in tree holes in Illinois and South Carolina. Decaying gill fungi and rotted puffballs have yielded it in Indiana, Kentucky, Maryland, Iowa, Illinois, and Massachusetts. The beetles prefer carrion over rotting fruits; Pirone (1974) took 462 specimens at fish carrion and only three at rotting melon in New York; Walker (1957) found this species only at fish carrion and not at rotting cantaloupe or cornmeal baits in Tennessee. Single occurrences in unusual places have been made under a kitchen sink in a Massachusetts house, in syrup traps in Virginia, by beating vegetation in Indiana, and from a tanglefoot screen and at blacklight in South Carolina. P. opaca has been abundantly taken in the southern part of its range on carrion baits in cave habitats. I have observed the beetle in large and persistent populations feeding on moist bat guano and carcasses in Kentucky, and Florida, and Black (1971) (Holsinger and Peck, 1971). Iowa. Jackson Co., Barred  Seasonal activity. Data on specimen labels show the species to be active from March through November, in both northern and southern locations, with most specimens being taken from May to September. Generally, the more southerly populations are active earlier and later in the year. A few studies have experimentally followed the changes in abundances of the species throughout the year. Pirone (1974) found the species to be the most common catopid on carrion in southern New York; the beetles occurred from mid April through to November, and most were taken in August. Shubeck (1969), in a three year study in New Jersey, found the species to have differing abundances through the summer but to be most common in early-middle summer. In a repeat study in the same forest (Shubeck, Downie, Wenzel, and Peck, 1977)the species was again found from April to November, with a midsummer peak in abundance. In Tennessee, Reed (1958) collected the beetle on dog carcasses from mid June to late August. In another Tennessee study, Walker (1957) took P. opaca in midsummer, but did not trap at other times. In a carrion study in an Illinois forest, Johnson (1975) found the beetle to appear in April and to be present through November, being most abundant in September. Larvae appeared at the end of the decay stage and were mostly associated with the dry stage; they occurred in May, were most common in July, and last appeared in September.
During one of his trapping programs in a New Jersey forest, Shubeck (1971)  Reproduction. Larvae for the species have been long known, and are illustrated in Boving and Craighead (1931). Although it should not be difficult to keep and rear the beetles (methods in Peck, 1973Peck, , 1975 I know of no data on eggs, egglaying, or larval stages and their biology, other than Johnson's (1975) observation that larvae are most commonly associated with the dry stage of decomposition.
Evolution and Biogeography. The distribution of Prionochaeta and of other members of the Cholevini suggests that they originated in the Old World. Probably only one species of Prionochaeta migrated into the New World across a Bering land bridge in the Tertiary (see Hopkins, 1967, for a discussion of the Tertiary Bering Bridge). Although the genus must then have lived in western North America, it became extinct there (probably by the Pleistocene), and survived only in eastern North America. The resulting generic distribution in eastern North America and in eastern Asia is a not uncommon type of disjunct pattern (Darlington, 1957). It is believed here that the abundance of cave populations in the southern part of the species range is a reflection of distributional adjustments in the present post-glacial. Since the beetles apparently require a cool and moist temperate habitat, as climatic conditions have warmed, the beetles have become less able to survive in the now less-temperate southern forests where they lived during the Wisconsinan glacial. Caves, with their seasonally more uniform, cool and moist conditions, have thus become Recent southerly refugia for this beetle (although some southern forest populations yet remain) as they have for several other insects (Peck and Russell, 1976