Abstract
Cannibalism, the act of eating an individual of the same species has been little studied in omnivorous insect predators. Dicyphus errans (Wolff) (Hemiptera: Miridae) is a generalist omnivorous predator that commonly occurs in tomato greenhouses and field crops in the Mediterranean basin. In this work cannibalism among same-aged neonate nymphs of D. errans was studied when 1, 2, 4, 8 or 16 individuals were placed in a Petri dish along with or without heterospecific prey. Although nymphs were unable to complete their development in the absence of prey they survived longer when there were initially 2 individuals per dish than in any other treatment including a single individual. This may indicate that cannibalism in this predator has positive effect on nymphal survival, which however was not the case at higher densities. The presence of heterospecific prey increased nymphal survival and individuals were as equally successful in completing their development as when kept singly. Developmental time in all the treatments was very similar. Adult weight of both females and males was significantly greater when a nymph was reared alone and similar in all the other treatments. The results indicate that cannibalism occurs among neonates of D. errans if heterospecific prey is scarce and has a negative effect on adult weight when heterospecific prey is abundant. This should be considered in studies on enhancing the biocontrol efficiency or mass rearing of this predator.
Highlights
Cannibalism, the process of killing and consuming a part or all of a conspecific occurs in a wide range of carnivorous as well as in phytophagous arthropods (Fox, 1975; Polis, 1981; Woodward & Hildrew, 2002; Richardson et al, 2010; Booth et al, 2017)
Studies on intraspecific interactions in arthropods have revealed that density and food availability are among the important factors affecting the occurrence of cannibalism (Fox, 1975; Polis, 1981)
In the present study we show that the incidence of cannibalism in the omnivore, D. errans is correlated with the availability of heterospecific prey
Summary
Cannibalism, the process of killing and consuming a part or all of a conspecific occurs in a wide range of carnivorous as well as in phytophagous arthropods (Fox, 1975; Polis, 1981; Woodward & Hildrew, 2002; Richardson et al, 2010; Booth et al, 2017) This behaviour may enhance fitness of cannibals in periods of food scarcity by providing them access to high quality nutrients, reducing competition or decreasing the risk of predation and/or parasitism (Fox, 1975; Polis, 1981; Gabriel, 1985; Van den Bosch et al, 1988; Agarwala & Dixon, 1992; Elgar & Crespi, 1992; Henson, 1997; Gagné et al, 2002; Michaud, 2003; Claessen et al, 2004; Booth et al, 2017). Cannibalism is influenced by the strength of intraspecific competition, mating status, habitat structure and hunger level (Polis, 1981; Wise, 2006)
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