Data from: Humidity modifies age-dependent heat wave effects in an insect host-parasitoid interaction

Climate change is projected to increase the likelihood of extreme heat
events, but it may also increase humidity levels, leading to the potential
for coupled thermal and hydric stress. While increasing frequency and
intensity of extreme heat events have been well-documented for their
negative effects on species and their interactions, how humidity modulates
the impacts of heat stress is currently unknown.  We investigated
how humidity interacted with heat stresses of different timings and
durations to affect the life histories in an insect host-parasitoid
interaction, comprising the Indian meal moth, Plodia
interpunctella, and its endoparasitoid wasp, Venturia canescens. Hosts
parasitised as 4th instar larvae and unparasitized hosts were maintained
in a high humid (60.8% RH) or low-humid (32.5% RH) environment at a
constant temperature of 28℃. They were then exposed to 38℃ thermal
stresses with a duration of 6 or 72 hours in either the 4th or 5th instar.
Humidity and heat stresses did not affect the adult emergence of
unparasitized hosts, but longer heat stress and lower humidity increased
the probability that host adults emerged from parasitized hosts,
indicating the negative effect of these conditions on the survival of
parasitoids. Furthermore, juvenile development time and body size of hosts
and parasitoids responded differently to timing and duration of heat
stresses, and high humidity decreased larval development time of
unparasitized hosts and increased the size of both hosts and parasitoids.
In addition, humidity negatively interacted with larval stage and duration
of heat stress to affect the size of unparasitized hosts, but this effect
was not found in parasitoids. Our results show that humidity modulates the
life history of hosts and parasitoids, highlighting the importance of
humidity in maintaining host-parasitoid interactions. Humidity should be
considered when predicting the impact of temperature extremes on species’
population dynamics and their interactions.