sufficient to analyze the cloud forest fauna at Zurqui
de Moravia, equivalent in habitat and elevation to
Monteverde. Although fewer than half as many speci-
mens have been seen from Zurqui as from two low-
land sites (La Selva Biological Station and the Osa
Peninsula, 0—200 m), Zurqui has produced as many
or more species. About one-third of the species col-
lected in Zurqui thus far are new to science. The
Zurqui samples were dominated by corthyline and
platypodid ambrosia beetles (70% and 25% of ambro-
sia beetle individuals, respectively). Although many
corthyline species were present in the lowlands (21
of 57 species at La Selva, 9 of 59 at the Osa Peninsula),
none was common in Malaise samples. Rather, low-
land site collections were dominated by ambrosia
beetles of the tribe Xyleborini; only a few xyleborines
were trapped at Zurqui. The ecological replacement
of xyleborines by corthylines at higher altitudes was
also documented in Mexico (Noguera-Martinez and
Atkinson 1990). The ambrosia beetle communities of
Zurqui and other mid- or high-altitude sites in Costa
Rica (L. Kirkendall, unpubl. data) are overwhelmingly
composed of outbreeding species, whereas the vast
majority of ambrosia beetle species at La Selva, less
than 50 km away, practice regular mother-son or
brother-sister mating.
Specimens from Zurqui were more evenly distrib-
uted among species than were those at low-altitude
sites. For example, two species of Monarthrum and
one species of Tesserocerus each made up 8—15% of
the catch; at La Selva, 48% of all specimens were
Xyleborus affinis, and 10% were Xylosandrus mori-
gerus. Although Zurqui and La Selva share 10 of 14
ambrosia beetle genera, only seven species were com-
mon to both sites. The five most frequently trapped
Zurqui species have only been found at middle or
upper altitudes. Of the five most frequent La Selva
species, only Megaplatypus discicollis was also com-
mon at Zurqui; the other four were common only at
low altitudes in Costa Rica and elsewhere. As with
many other insects, altitude is a major factor affect-
ing species distributions (Stevens 1992).
Since ambrosia beetles are seldom host specific,
the existence of this species-rich community of gen-
eralists seems paradoxical. Ambrosia beetle/fungus
partnerships may be specializing on environmental
factors rather than host plant taxa. "Nonequilibrium"
ecological models may explain coexistence of several
to many ecologically similar species on the same re-
source when that resource is patchily distributed and
difficult to find. That situation may apply to ambro-
sia beetles dependent on sporadic branch or tree falls
for their sustenance (Beaver 1977, 1979b). Competi-
tive exclusion among ecologically similar species may
be prevented by the patchy distribution and ephem-
eral nature of the habitats (Ricklefs and Schluter 1993,
Hanski 1994).4.5. Lepidoptera: Moths and Butterflies4.5.1. Introduction
Paul Hanson
Moths and butterflies (order Lepidoptera) rank sec-
ond only to birds in popularity among ecotourists.
Their larvae represent the largest group of plant-feed-
ing animals. Caterpillars are one of the most impor-
tant food resources for insectivorous birds, as are adult
moths for bats. Lepidoptera are also ideal organisms
as environmental indicators (Holloway 1985).
In Costa Rica, there are at least 80 families and an
estimated 13,500 species of Lepidoptera, which is
comparable to the fauna of America north of Mexico.
The largest families (at least 500 species in the coun-
try) are Gelechiidae, Tortricidae, Pyralidae, Geome-
tridae, Notodontidae, Arctiidae, and Noctuidae
(J. Corrales and E. Phillips, pers. comm.). Species of
Costa Rican butterflies belonging to the families
Papilionidae, Pieridae, and Nymphalidae are covered
in DeVries (1987) and a checklist of species occurring
in Monteverde is in DeVries (1983). Some of the more
commonly observed butterflies at Monteverde include
morphos (Morphinae), swallowtails (Papilionidae),
monarchs (Danainae), Manataria maculata (see Sec.
4.5.3), and Heliconius clysonimus (Heliconinae). The
latter is the only Costa Rican species of Heliconius
restricted to higher elevations (800-1800 m).
Although the majority of lepidopterans are moths,
our knowledge of these families is incomplete, al-
though a checklist of sphinx moths (Sphingidae) in
Monteverde exists (Haber 1983). In Costa Rica, stud-
ies are being carried out on Limacodidae, Tortricidae,
Pyralidae, Geometridae, and Saturniidae. Tortricidae,
especially the subfamily Tortricinae, appears to reach
its maximal diversity at mid-altitudes in Costa Rica
(J. Powell, pers. comm.); research is needed to docu-
ment similar distribution patterns in other families of
moths.4.5.2. Migration of Butterflies
through Monteverde
Rob Stevenson & William A. Haber
More than half of the butterflies recorded in Monte-
verde are migrants (360 out of 658 species). These
butterflies leave the Pacific slopes and lowlands at the
end of the wet season when the quality of their larval
host plants and other resources in their habitat begin
to decline (Haber 1993). About 80% of the Pacific118 Insects and Spiders