Episodes of unpalatable prey reduce consumption and growth of juvenile praying mantids

Christopher J. Paradise and Nancy E. Stamp

ABSTRACT

Third instar praying mantids (Tenodera sinensis Saussure: Mantidae) were fed either a sequence of unpalatable milkweed bugs (Oncopeltus fasciatus Dallas: Lygaeidae) and palatable fruit flies (Drosophila melanogaster Meigen: Drosophilidae) or a control diet of palatable flies only. Mantids fed a sequence of three days of unpalatable bugs and four days of palatable flies took on average 5 days longer to develop to the fourth instar than the controls and, consequently, their growth rate was less than that of the controls. They ate 10-15 unpalatable bugs in that time, but also, because the stadium was prolonged, they ended up eating as many flies as the faster growing controls and therefore attained similar biomass. Mantids subjected to episodes of two days with unpalatable bugs followed by four days of flies had reduced growth rates that were a function of both more time spent in the stadium and less weight gained than the controls. Mantids subjected to episodes of one day with unpalatable bugs followed by four days of flies did not gain as much weight as the controls but had similar growth rates. Mantids fed unpalatable bugs on Days 1 and 6 and palatable flies on the other days and mantids fed flies for four days and then one day without food grew at the same rate. In this case, eating unpalatable prey for two days out of 7 (with 7 days = average stadium duration) slowed weight gain as much as missing food for a day. We conclude that, depending on the sequence, episodes (in this case one or more days) of eating unpalatable prey can reduce daily rate of consumption sufficiently to have a negative impact on biomass gained, stadium duration, and growth rate.

Key words

Invertebrate predator, consumption rate, growth rate, prey variability, Tenodera sinensis, Oncopeltus fasciatus.

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