Effect of temperature on the post-diapause development rate, survival, and body mass of the solitary wasp Isodontia elegans

We examined the relationship of post-diapause rearing temperature to
developmental rate, survival, and adult body mass of the solitary wasp
Isodontia elegans using prepupae from trap-nests. Isodontia elegans is a
member of a genus often found in trap-nests in North America and Europe.
Trap-nests are commonly used tools for studying cavity-nesting solitary
wasps and bees. In temperate zones, progeny in nests usually overwinter as
fully prepupae before pupating and emerging as adults. An important aspect
of properly using trap-nests is determining temperatures that affect
survival and health of developing offspring.  After overwintering
>600 cocoons containing prepupae after the summers of 2015 and
2016, we placed cocoons on a laboratory thermal gradient where offspring
experienced one of 19 constant temperatures from 643°C; emergence of
adults was monitored for 100 days.  Our conservative estimate for
the critical thermal minimum for development is 14°C, whereas that for the
critical maximum is ~33°C. Prepupae transitioned to adults most rapidly at
29–33°C, but developmental rate was lower for some progeny exposed to
temperatures ≥30°C. Offspring successfully reached the adult stage in
<100 days at of temperatures of ~19–33°C. Adults from cocoons
reared at lower temperatures weighed on average 6-10% more than expected
based on their head widths, whereas those reared at higher temperatures
weighed 4–10% less than expected. The difference may be due to greater
rates of water loss and lipid metabolism during development at higher
temperatures. Pre-overwintering cocoon mass was a significant predictor of
relative adult body mass, indicating that adult health is partly related
to their condition before overwintering. The trends we observed were
similar to those for the bee Megachile rotundata, which we previously
studied on the same gradient apparatus. However, data are needed on many
other species of wasps and bees from a diversity of
environments.