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Modeling Arthropod Predation: Wasteful Killing by Damselfly Naiads
Author(s) -
Johnson Dan M.,
Akre Barbara G.,
Crowley Philip H.
Publication year - 1975
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936148
Subject(s) - predation , damselfly , foregut , biology , instar , daphnia magna , functional response , arthropod , ecology , midgut , heteroptera , zoology , invertebrate , daphnia , aposematism , predator , larva , crustacean , anatomy , chemistry , organic chemistry , toxicity
Damselfly naiads were fed Daphnia magna in laboratory predation studies. Anomalagrion hastatum predation rates were highest during the first 2 days of the penultimate instar and then declined until ecdysis. The functional response of final instar Ischnura ramburii was most sensitive to changes in Daphnia densities of 5—50/liter. Many more prey were killed than eaten in both studies; this wastefulness increased significantly as densities rose from 5 to 10/liter. Observations of feeding behavior revealed that damselfly naiads frequently strike at and capture prey and then discard them uneaten or only partially eaten. This is presumed to be the proximate cause of wasteful killing. Photographic documentation of gut contents showed that during feeding the foregut often becomes full before the midgut, leading us to hypothesize that wasteful killing occurs when hunger in the midgut motivates capture, but fullness of the foregut precludes eating. When wasteful killing is a normal component of hunger—motivated feeding behavior, it has sometimes been explained by hypothesizing the existence of a hunger threshold which is higher for eating than for capture (Holling 1966). We propose a two—gut—compartment formulation of Holling's simultion model of invertebrate predation which accounts for dynamic characteristics of wasteful killing without hypothesizing an elevated hunger threshold for eating.