742 specimens). Three subfamilies, Tachyporinae (66
species), Osoriinae (58 species), and Oxytelinae (35
species), contain a moderate number of species. Rela-
tively few species are found in Megalopiniae (13 spe-
cies), Piestinae (10 species), Steninae (10 species),
Proteininae (5 species), and Euaesthetinae (3 species).
Four subfamilies (Micropeplinae, Pseudopsinae, Oxy-
porinae, Omaliinae) contained only one species each.
Distribution of staphylinid species is not uniform
within Monteverde. We divided the region into three
areas: (1) 1200-1500 m on the Pacific side, (2) 1500-
1800 m on the Pacific side, and (3) 800-1400 m on
the Atlantic side (Pefias Blancas valley; Fig. 1.4). We
collected 270 species from area 1 (118 species exclu-
sive to area 1), 475 species from area 2 (297 species
exclusive), and 292 species from area 3 (190 species
exclusive). Areas 1 and 2 shared 90 species, and areas
2 and 3 shared 40 species.
The most diverse set of microhabitats were those
associated with fungi (134 species total, 68 species
found exclusively in this habitat), followed by forest
litter (132 species total, 52 exclusively) and subcorti-
cal habitats (85 species total, 34 exclusively).
Staphylinids living under bark. The subcortical (under
bark) habitat is complex and dynamic. Its character-
istics depend on the kind of tree, the time since the
tree has fallen, and local microclimatic conditions.
Bark in different parts of a log are often in different
stages of decay, so a diversity of staphylinid subcor-
tical communities can occur on the same log, some-
times within a few centimeters of one another.
The most diverse subcortical staphylinid commu-
nity is found under bark of recently fallen trees on
which the cambium has begun to ferment, with
slightly loose bark. The staphylinid community is
characterized by specialized predatory staphylinids:
xantholinines (e.g., Homalolinus spp., Ehomalolinus
spp., Heterolinus), a few distinctive species ofBelo-
nuchus (e.g., B. dichrous), and Holisus. The commu-
nity also includes a diverse array of staphylinids that
are saprophagous or feed on fungi in the fermenting
cambium: Piestus (Zirophorus), Hypotelus', several
genera of osoriines (Eleusis, Renardia, Leptochirus,
Priochirus, Lispinus, Nacaeus, and Clavilispinus), sev-
eral aleocharines (Placusa, expected but not yet re-
corded from Monteverde, and Homalota), and the
tachyporine Coproporus.
The subcortical habitat with fermenting cambium
slowly transforms into a less rich habitat as the avail-
able carbohydrates are used by bacteria, fungi, and
saprophagous arthropods. These communities are
usually dominated by saprophagous staphylinids; for
example, adult and larval osoriines (especially Lepto-
chirus, Priochirus, Lispinus, Nacaeus, and Thora-
cophorus) can be abundant in such logs. Species of
Piestus (sensu stricto), the paederine Sunius, and
falagriine aleocharines such as Myrmecocephalus are
found under bark. Bark of very old logs in which the
subcortical spaces are filled with dense masses of very
decayed frass and mud-frass mixtures have few sta-
phylinids. Some of these logs may contain colonies
of the cylindrical osoriine Osorius.
The most striking modification among subcortical
staphylinids is in body shape, which takes two forms:
highly flattened, or slender and cylindrical. Members
of the genus Leptochirus are common subcortical
staphylinids in Monteverde. These are large (2 cm or
more in length), usually shining black, with broad and
very flattened head, prothorax, and elytra; the abdo-
men is cylindrical and forms a rigid tube for strength.
Species of Priochirus have a similar body form. Al-
though these two genera are not closely related, it
is difficult to distinguish them. In Monteverde, all
Priochirus have short cephalic horns, which are ab-
sent in Leptochirus.
Another frequently encountered and strikingly flat-
tened staphylinid is the xantholinine Homalolinus.
The most commonly encountered species, H. canali-
culatus, is more than 2.5 cm long and has a shining
black, flattened body, with the tip of the abdomen red.
The broad, flattened, arrowhead-shaped head and
narrow neck are distinctive. The most flattened sta-
phylinids are osoriines in the genus Eleusis, which
have paper-thin bodies. Other staphylinids that have
strongly flattened bodies include the piestines Piestus
and Hypotelus, the osoriine Renardia, and the aleo-
charines Placusa, Homalota, and Cephalaloxynum.
Life histories of subcortical staphylinids have not
been investigated. The confined spaces of this habi-
tat may place considerable constraint on life history
traits; for example, larvae of instars, pupae, and adults
of osoriines (particularly Leptochirus and Priochirus)
are found together under bark, suggesting that they
may be subsocial. I once encountered colonies of
Osorius under very decayed bark in which the sub-
cortical space was filled with a soillike mixture of
mud and frass. The colony consisted of independent
radiating tunnel systems without obvious connections
between them. Within each tunnel system were two
adults (presumably male and female), an egg at the
terminations of most radiating tunnels, and larvae and
pupae of all stages, a pattern expected for subsocial
insects.Staphylinids associated with rodents. One of the most
unusual groups of rove beetles is the tribe Am-
blyopinini. Adults are found in the fur of many
rodents and some marsupials in Central and South
America. They are relatively large (1 cm or more in109 Insects and Spiders