Effect of food shortage on the post-embryonic development and reproductive potential of Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) in the laboratory

The consequences of food shortage on the post-embryonic development and reproductive potential of Chrysoperla externa (Hagen) in the laboratory were evaluated. First, second, and third instar larvae received only food on the 1.st, 2.nd, or 3.rd day after ecdysis. During the periods that preceded or followed the tests in the corresponding instars, the larvae received one, two, and three feeding units (FU) at every two days for the 1.st, 2.nd, and 3.rd instars, respectively. Each FU consisted of a cardstock disc containing Sitotroga cerealella eggs (Lepidoptera: Gelechiidae). Daily evaluations included survival in the different instars and in the larval and pupal stages, as well as the pre-oviposition and oviposition periods, plus number and viability of eggs. The results showed that food shortage during the 1st instar could be offset during larval development. However, the larvae must find food in their first 48 hours of age, because survival in that instar gradually decreased in the absence of food, and 100% mortality may occur when the larvae do not feed until 48 hours after hatching. The pre-oviposition and oviposition periods, as well as fecundity, were not influenced by food shortage during the 1st larval instar. C. externa larvae require a protein-rich diet during the 2.nd and 3.rd instars, since the ingestion of water and sugars alone during these stages caused high larval mortality. However, fecundity and egg viability were not affected by food shortage during the studied instars.

biological control; chrysopid; feeding regime; predator


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