Carnivorous Plants and Their Prey

Pitcher-plant midges, for example, appear to choose pitchers with more fluid while pitcher-plant
mosquitoes may select pitchers of a certain age (80). Plant position within a site also influences
colonization. Pitchers near adult dipteran feeding or mating sites tend to receive more larvae than
those pitchers that are less closely located (77). Some pitchers probably enjoy greater inquiline
insect colonization by simply being more readily accessible, too (76). Even seemingly minor
points of dissimilarity in plant position can lead to significant variations in pitcher microclimate
(76, 77, 80). Pitchers in full sun, for example, may dry out more readily than those in shady sites.
As pitcher fluid dissipates, the inquiline community can be extirpated (80). Similarly, pitcher
temperatures can vary from favorable to lethal for larvae within a small geographic location (77).
Temperature effects on survivorship of larvae is unclear however (77, 81).
Whether across sites or within individual plants, pitcher selection by ovipositing insects
appears to be ultimately a function of potential prey capture in the host pitcher. This, in turn, is
related to the accumulation of organic material (81). Larvae are more likely to survive in pitchers
with sufficient amounts of food and pitcher fluid (80). As pitchers age, they tend to capture more
prey lending to increased larval survivorship in those pitchers. There appears to be an optimal
age to pitchers for insect colonization however (77, 80). Ovipositing pitcher-plant mosquitoes,
for instance, prefer newly produced pitchers to those from the previous season’s growth (80). As
Sarracenia purpurea pitchers age, insect capture rates tend to decline as do dipteran colonization
rates (77). Larger pitcher leaves catch greater amounts of prey and are preferentially selected by
dipteran mutualists (77, 80, 81). Although poorly understood, dipteran females like pitcher-plant
mosquitoes may choose oviposition sites through the use of some chemical attractant found in
pitcher fluids. Characteristics such as hood shape or color do not appear to influence pitcher
selection by these dipterans significantly (80).
Ovipositing pitcher-plant mosquitoes, midges, and flies preferentially prefer pitchers that
will provide their offspring with suitable habitat and sufficient food supplies (77, 80). Following
colonization decisions, microclimate coupled with food availability dictates survivorship of
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