Monteverde : Ecology and Conservation of a Tropical Cloud Forest

Table 4.2. Numbers of Mischocyttarus mastigophorus colony types and adults of two

color morphs at different elevations in Monteverde.

Elevation (m)

1475-1499 1500-1524 1525-1549 1550-higher

Colony type^3

All pale

Mixed

All dark

Number of adultsb

Pale

Dark

11(8)

1

0

69(8)

2

0

0

0

0

0

3

7(3)

1

76 (22)

50(9)

4(1)

5

0

133 (64)

32 (18)

Colony types: all pale, only pale morph adults present; mixed, pale and dark morph adults present; all dark,

only dark morph adults present.

Colony types differed in relative abundance at different elevations (likelihood ratio C^2 = 12.90, df = 4, p < .05;

Fienberg 1989); colonies containing dark morph adults were more common at higher elevations. The color morphs

differed in relative abundance at different elevations (likelihood ratio C^2 = 47.21, df = 2, p < .001); dark morph

wasps were more abundant at higher elevations.

aNumbers of pre-emergence nests (foundress associations that had not yet produced adult offspring) are given in

parentheses.b

Numbers of males are given in parentheses.

The fact that pale and dark morph adults can emerge
from a nest on the same day suggests that the poly-
morphism has a genetic basis, but environmental
determinants such as temperature or food intake can-
not be ruled out. How did two discrete morphs of
M. mastigophorus evolve? It is possible that the morphs
were formerly isolated. Data on differential survivor-
ship of the M. mastigophorus morphs with elevation
are needed to assess whether there is selection for
different morph frequencies, which could maintain
the polymorphism at Monteverde.
Dark-bodied insects are likely to warm to flying
temperature more readily than pale-bodied conspe-
cifics in cool climates. Body colors of other vespid
wasps suggest that selection for efficient thermoregu-
lation could play a role in establishing the elevational
patterns of morph frequencies. Some species of Ves-
pidae exhibit reduced pale markings in populations
at higher elevations, but this variation is more subtle
than the M. mastigophorus morph color differences.
The degree to which this Mischocyttarus/Agelaia
mimicry complex is driven by Batesian versus Miil-
lerian selection is unknown. Since M. mastigophorus
appears to be rare relative to both model species, its
presence is unlikely to select strongly for changes
in Agelaia spp. color patterns. We hypothesize that
M. mastigophorus, and other species of Mischocyt-
tarus, are effectively Batesian mimics. Mischocyttarus
mastigophorus nests are often located in sheltered,
dark sites. Mimetic protection may accrue mainly
to foragers in the field rather than to the nests
themselves.

Acknowledgments Eva Chun first noted the exis-

tence of two M. mastigophorus color morphs and

called our attention to this fascinating species. Mary

Jane West-Eberhard and Jim Carpenter generously

aided in identification of the wasps. We thank the

Monteverde Cloud Forest Preserve and the Monte-

verde community for assistance and permission to

collect specimens.

4.7.5. The Ants of Monteverde

John T. Longino

Ants are not a conspicuous feature of the Monteverde

landscape. There are occasional marauding army ants,

pest ants that inhabit dwellings, and leafcutting ants

that plague the garden or even come into the kitchen

to steal food. In contrast to lowland sites, ants do not

drip from the vegetation, nor do they teem across the

ground; in the cold wet cloud forest itself, one could

easily conclude that there are no ants. In reality, no

place in Monteverde is truly ant-free. Even the wet,

windswept elfin forest, which appears to be an in-

imical habitat for ants, is home to a set of species, al-

beit relatively few (Longino and Nadkarni 1990). As

one descends in any direction, ant species richness

increases.

Based largely on my collecting experience in Monte-

verde from 1983 to 1996, this overview of Monteverde

ants highlights common and conspicuous species in

six groups: (l) army ants, (2) leafcutting ants, (3) pest

ants, (4) large predacious ants, (5) ants of cloud for-

est leaf litter, and (6) ants of the cloud forest canopy.

132 Insects and Spiders