Figure 4.3. Milkweed bugs (Lygaeidae), order Hemiptera. Photograph by Gregory Dimijian.ter habitats include backswimmers (Notonectidae),
giant water bugs (Belastomatidae), creeping water bugs
(Naucoridae), water striders (Gerridae), and ripple bugs
(Veliidae). The latter two families are semiaquatic and
skate rapidly over the surface of water. In the Monte-
verde area, intraspecific competition has been stud-
ied in Rhagovelia scabra (Veliidae) in the Rio Guacimal
(Wilson et al. 1978). Adult females predominate in
fast-flowing areas of the stream at the head of pools,
which contain more food (dead insects floating on the
water surface) than the quiet margins of streams, where
juveniles are found. The mechanism behind this spa-
tial distribution appears to be interference; ripple bugs
spend a lot of time chasing each other.
Homoptera. Spittlebugs, cicadas, leafhoppers, tree-
hoppers, whiteflies, aphids (Fig. 4.4), scale insects,
and their relatives feed almost exclusively on plant
sap. These insects are highly specialized for penetrat-
ing living tissue and imbibing a liquid diet. Just as
mosquitoes transmit animal viruses, homopterans are
the most important vectors of viral diseases of plants.
Some species feed primarily on plant mesophyll tis-
sue; others tap either xylem or phloem. Xylem car-
ries water up from the roots and is under relatively
low pressure; xylem-tapping homopterans (spittle-
bugs, cicadas, and some leafhoppers) excrete large
quantities of water and often have a bulging face that
contains well-developed muscles used in pumping.
Phloem carries sugars produced by photosynthesis
and is under greater pressure; phloem-tappers excrete
a sugary honeydew and usually have a more concave
face. The honeydew excreted by phloem feeders at-
tracts ants and other insects that can protect these
homopterans from their enemies.
Homoptera is divided into two subgroups: Auche-
norrhyncha (planthoppers, spittlebugs, cicadas, leaf-
hoppers, and treehoppers) and Sternorrhyncha (psyl-
lids, whiteflies, aphids, mealybugs, and scale insects).
The former are larger, stouter, more active insects, and
most adults jump when disturbed, hence the name
"hopper." The latter tend to be smaller, more fragile,
and less mobile; only psyllids are active jumpers.
Scale insects are highly specialized plant parasites
that often remain attached to one site for most of their
lives. They typically secrete a waxy scalelike cover-
ing and are often not recognized as insects.
In Costa Rica, there are at least 40 families of
Homoptera. The largest families include the Cixiidae
(plant hoppers), Delphacidae (plant hoppers), Derbi-
dae (plant hoppers), Cicadellidae (leafhoppers), Mem-
bracidae (treehoppers), Pseudococcidae (mealybugs),
and Diaspididae (armored scales). Cixiid nymphs
usually feed on roots of plants (especially grasses);
nymphs of many derbids feed on fungi associated
with rotting wood.
In Costa Rica, Auchenorrhyncha have been better
studied than Sternorrhyncha. One of the best-known100 Insects and Spiders