from parasitoids (principally Cynipidae and several
Chalcidoidea) and predators (a few ants and vespids,
and virtually all bees).
In Costa Rica, cynipids (gall wasps) are exclusively
associated with oaks (Quercus, Fagaceae). All species
are undescribed, and their biology has received little
attention. Many induce gall formation on leaves,
twigs, flowers, fruits, and roots, but others are in-
quilines, which feed on gall tissue induced by other
species of cynipids. Species that form galls have a
sexual generation (with both sexes) and an asexual
generation (females only). Females from the two gen-
erations are morphologically different and induce
completely different galls (Askew 1984); an oak tree
that has 20 different types of galls probably has only
10 species of gall-forming cynipids. Associating the
two generations of each species is an essential first
step in life history studies but requires cage experi-
ments or molecular techniques.
Phytophagy has evolved several times in the super-
family Chalcidoidea: Agaonidae (fig wasps), Tanao-
stigmatidae (associated with galls on legumes), Mega-
stigmus (Torymidae), and others (Hanson and Gauld
1995). Most Tanaostigmatidae are gall-formers, al-
though at least one Costa Rican species (Tanaostigma
couTsetiae] is an inquiline in psyllid galls on Lon-
chocarpus atropurpureus (Leguminosae). Tanaoneum
darwini is known only from Monteverde; although its
host there is unknown, other Costa Rican species be-
longing to this genus induce galls in the aril surround-
ing the seeds oflnga (Leguminosae). Larvae of Mega-
stigmus feed in seeds of Ilex (Aquifoliaceae) and
Symplocos (Symplocaceae).
Bees evolved from predatory sphecid wasps. Their
biology resembles other sphecids except that the female
provisions the nest with pollen, nectar, and other flo-
ral resources rather than arthropod prey. Groups that
nest in the ground include Colletinae, Diphaglossinae,
most Halictinae, Andreninae, Anthophorinae, and Bom-
binae. Groups that nest in cavities or hollow twigs in-
clude Hylaeinae, Xeromelissinae, Augochlora (Halic-
tinae), Megachilinae, Xylocopinae, Euglossinae, and
Meliponinae. The biology of only few cloud forest spe-
cies has been studied, including Crawfordapis luctuosa
(see Sec. 4.7.6), Ptiloglossa guinnae (Roberts 1971), Pseu-
daugochloropsis graminea, P. sordicutis (Michener and
Kerfoot 1967), Deltoptila spp. (LaBerge and Michener
1963), Ceratina ignara (Michener and Eickwort 1966),
Bombus ephippiatus (Heithaus 1983), and Meliponi-
nae (see Sec. 4.7.7). As in Sphecidae, cleptoparasitism
has evolved in certain groups of bees; in Costa Rican
cloud forests, these include at least four genera. Eusocial
behavior has evolved in bumblebees (Bombinae), sting-
less bees (Meliponinae), and the introduced honeybee
(Apinae). Keys to the genera of North and Central
American bees are in Michener et al. (1994). The biol-
ogy of tropical bees is described in Roubik (1989).The color of cloud forest hymenopterans. High altitude
species of cloud forest hymenopterans are generally
less brightly patterned than their lowland counter-
parts. Groups that contain gaudily colored species
decrease in species richness with increasing altitude.
For example, the speciose chalcidid genus Conura,
whose members are predominantly patterned with
yellow and black, is common in lowland clearings but
scarce in cloud forests. In other groups (e.g., Cryptini
[Ichneumonidae]), the cloud forest species are darker
and more drably colored than their lowland relatives.
This trend is particularly strong in nest-building taxa
such as sphecids and bees, where there may be a
greater need for thermoregulation (see Sec. 4.7.2).
Dark color is presumably an adaptation that allows
these hymenopterans to absorb radiant energy rapidly
when the sun is shining.
Another factor that affects color pattern is mimicry.
The color of cloud forest hymenopterans may be par-
tially determined by the availability of models. For
example, Dolichomitus annulicornis (Ichneumoni-
dae) appears to be a Batesian mimic of species of
Agelaia (Vespidae). Apechthis species (Ichneumoni-
dae), which emit a disagreeable odor when handled,
are Miillerian mimics of Neotheronia species, ich-
neumonids that have tarsal claws armed with poison
glands. Many conspicuous vespid models in the low-
lands, and their mimicry complexes, are absent in
cloud forests. There are fewer mimics of predomi-
nantly yellow-colored vespids, because these models
reach the upper end of their altitudinal distribution
in cloud forests (see Sec. 4.7.3).
A common color pattern in the lowlands is black
head, reddish orange thorax, and black abdomen.
Although the model is not known, this color pattern
occurs in diverse taxa, including a few nonhymenop-
terans. In the lowlands, species belonging to 12 gen-
era of Scelioninae (Scelionidae) show this striking
color combination. Only eight of these genera occur
in cloud forests, where most of them reach the upper
limits of their distribution: Baryconus, Chromoteleia,
Lapitha, Oethococtonus, Probaryconus, Scelio, Scelio-
morpha, and Triteleia. More study is needed to docu-
ment and explain the altitudinal distribution of color
patterns in Hymenoptera.4.7.2. Distribution Patterns of Cloud Forest
Hymenoptera in Costa Rica
Ian D. Gauld & Paul Hanson
In Costa Rica, most hymenopterans tend to be re-
stricted to one or sometimes two of three broad alti-126 Insects and Spiders