1988). Understanding how the distribution of cloud
forest leaf beetles relates to the distribution of their
food plants will help explain how high-altitude leaf
beetle fauna evolved. The mosaic of habitats at the
edge of reserves—old fields, secondary forest, and
patches of primary forest—generates a more diverse
leaf beetle fauna than unbroken primary forest. Main-
tenance of variegated buffer zones around protected
wildlands and prevention of high-intensity agricul-
ture from moving to reserve borders benefits both
conservation and tropical Chrysomelidae.
4.4.7. The Bark and Ambrosia Beetles
(Scolytidae and Platypodidae) of
Costa Rican Cloud Forests
Lawrence R. Kirkendall & Stephen L Wood
Bark and ambrosia beetles (Scolytidae [or Curculio-
nidae-Scolytinae] and Platypodidae) tunnel in woody
plants. As with the Cerambycidae, they are primary
decomposers of dead woody tissues in forests. A few
temperate species have gained notoriety as tree-killers
of significant economic importance; in the tropics the
most important pest is the Coffee Berry Borer (Hypo-
thenemus hampei). The economic impact of other
tropical species is greatest from damage to logs by
ambrosia beetles; few scolytid or platypodid beetles
kill healthy trees.
In Costa Rica, about 500 species of Scolytidae
(Wood et al. 1992) and 58 species of Platypodidae
(Equihua and Atkinson 1987) are known or expected,
which represent two-thirds to three-fourths of the
actual number of species in Costa Rica. A total for the
two groups of 700-850 species would be at least 10%
of the approximately 7,300 species known worldwide
(Wood and Bright 1992).
All bark and ambrosia beetles feed and lay eggs
in tunnel systems, a habit shared with Bostrichidae,
Anobiidae, and a few weevil groups, but otherwise
rare in beetles. The term "bark beetles" refers either
to scolytids as a whole or to those taxa breeding (tun-
neling) in inner bark; "ambrosia beetles" encompasses
unrelated groups of scolytids and most platypodids,
all of which grow fungi on the walls of their tunnel
systems. The mutualistic fungi provide the major or
sole source of nutrition for adults and larvae (Beaver
1988).
Living in long-lasting defensible tunnel systems
has led to the evolution of an unparalleled variety of
social behaviors in these cryptic beetles (Kirkendall
1983, 1993, Noguera-Martinez and Atkinson 1990,
Kirkendall et al. 1997). Most scolytids and apparently
all platypodids are outbreeders, but extreme inbreed-
ing has evolved repeatedly and has proven success-ful; all xyleborines, for example, reproduce by brother-
sister or mother-son mating. In outbreeding species,
males stay for most or all of the oviposition period,
and in some species (including most platypodids)
males die with their mates. Some are monogynous
(most platypodids, many scolytids), but simultaneous
("harem") polygyny is common, and some groups are
regularly bigynous. Varying degrees of parental care
have evolved, ranging from protection from preda-
tors by males or females to apparently sterile female
"workers" tending the offspring of their mother, as in
an Australian platypodid (Kent and Simpson 1992,
Kirkendall et al. 1997). Parental behavior is complex
in all ambrosia beetles but has been little investigated.
Bark and ambrosia beetles vary in their degree of
host plant specificity, and overall are less host spe-
cific in the tropics than in temperate regions (Beaver
1979a). Tropical ambrosia beetles and their fungi are
thought to be only broadly host specific because dif-
ferences in biochemical and physical properties of
sapwood are minor.
Intensive Malaise trap sampling (P. Hanson and I.
Gauld; see Sec. 4.7; Fig. 4.12) has yielded materialFigure 4.12. Paul Hanson with Malaise trap at the
Zurqui study area. Photograph by Lawrence Kirkendall.117 Insects and Spiders