Data Beretta et al. 2024 Biological Control 188 105437. https://doi.org/10.1016/j.biocontrol.2023.105437

Biological pest control is successful in many agricultural systems, yet various pests can still not be controlled with
natural enemies. Examples are invasive thrips species such as Echinothrips americanus Morgan and Thrips parvispinus
(Karny) in Europe. The lack of biological control of these pests in several crops has been subscribed to
their complex life cycle and cryptic behaviours, but their antipredator behaviours may prevent successful control
and have not been studied extensively. One of these behaviours is the potential of thrips to kill the eggs of
predatory mites, which we quantified. Furthermore, we observed the behaviour of first- and second-instar thrips
larvae when attacked by starved predatory mites Amblyseius swirskii Athias-Henriot. For comparison, we included
Frankliniella occidentalis (Pergande), which shows an array of defensive behaviours, but can be controlled successfully
by several species of predatory mites. Second-instar larvae and adults of F. occidentalis and T. parvispinus
killed predator eggs, but E. americanus did not. First- and second-instar larvae of all three species swung their
abdomen to defend themselves, and F. occidentalis and T. parvispinus produced anal droplets, which are also
involved in defence. Predators were not successful in attacking any second-instar larvae during 15-minute observations,
which is sufficiently long for an attack. First-instar larvae of F. occidentalis and T. parvispinus were
sometimes successfully attacked by the predatory mite before they could mount a defence, but first-instar
E. americanus always defended themselves and were almost never preyed upon. Cooling thrips larvae to suppress
antipredator behaviour increased predation for all species and stages, except for first instars of
F. occidentalis. In conclusion, the lack of successful control of E. americanus is not caused by killing predator eggs,
but by the efficient defensive behaviour of both larval instars. Our study furthermore suggests that T. parvispinus
can potentially be controlled by A. swirskii.