Defense and Escape

Because they are among the most abundant phytophagous insects in many habitats, Auchenorrhyncha are an important food source for numerous vertebrate and invertebrate predators (see next section: Natural Enemies). Species of Auchenorrhyncha exhibit myriad strategies for avoiding predation. These range from relatively simple behaviors, such as dodging around to the opposite side of a leaf or branch as a predator approaches, or hiding under a leaf sheath, to complex mutualistic associations and mimicry. Adults of many species are strong flyers and nearly all (except cicadas) are also excellent jumpers. Juvenile (nymphal) cicadas, spittlebugs, treehoppers, and some planthoppers are incapable of jumping and have adopted other strategies for avoiding predators. All cicada nymphs and many spittlebug and planthopper nymphs are subterranean; thus, their exposure to most predators is minimal. Spittlebug nymphs live within masses of froth and machaerotid nymphs live in calcareous tubes cemented to the host plant. The free-living nymphs of most other auchen-orrhynchans appear to rely on cryptic coloration and body forms to escape detection by visual predators such as birds. For example, many treehopper nymphs are strongly flattened with the ventral surfaces of the body concave, enabling them to lie flat against the bark or leaf surfaces of their host plant. Others resemble plant parts such as bud scales or leaflets. Many plan-thopper nymphs secrete copious quantities of wax [Fig. 4(21)], with which they coat themselves and, often, surrounding parts of their host plants. The wax may prevent parasites and predators from grasping the nymphs, allowing them to leap away. Adults of some species mimic various venomous arthropods such as ants, wasps, robber flies, assassin bugs, and spiders. Some bear horns or spines on the pronotum [Membracidae, Fig. 3(15)] or scutellum [Machaerotidae, Fig. 1(2)] that make them physically difficult for some vertebrate predators to swallow. Many adult cercopids and membracids have conspicuous (aposematic) color patterns, presumably indicating that they are unpalatable. Others have the forewing apices marked with false eyespots, and a few (e.g., Fulgoroidea: Eurybrachidae) have prolongations resembling antennae; the head and thorax of such species often bear transverse lines resembling abdominal segmentation. Adults of various planthopper species mimic lizards, flowers, and lichens. Another strategy involves complex mutualistic associations with ants and other social hymenopterans. Ant mutualism has been documented in numerous lineages of Fulgoroidea and Membracoidea and occurs universally in some groups [e.g., tettigometrid planthoppers Fig. 4(20) and eurymeline leafhoppers]. In such groups, the nymphs usually form aggregations that are tended by ants. The aggressive worker ants drive off predators and receive gifts of honeydew, a sugary excretion, from the nymphs. Ant mutualism may have facilitated the development of subsocial behavior in some groups (see Membracoidea section under Diversity).

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