Associative learning of Podisus maculiventris (Hemiptera: Pentatomidae) to herbivore-induced plant volatiles

The spined soldier bug, Podisus maculiventris, is a polyphagous biocontrol agent that likely uses herbivore-induced plant volatiles (HIPVs) for foraging. We hypothesized that the behavioral responses of this predator to HIPVs are acquired via associative learning, as suggested by theoretical predictions linking natural enemy host range with odor preferences. We also proposed that it is possible to attract stink bugs to methyl salicylate (MeSA), if it is paired with a positive reward.

To evaluate P. maculiventris odor preferences, we combined laboratory and field experiments. First, naïve (i.e., lab reared in colony) and experienced (i.e., field collected) individuals were allowed to choose between scents released by caterpillar (Manduca sexta) damaged vs. undamaged tomato plants. In the second part, naïve adults and nymphs were conditioned to MeSA by linking this odor with M. sextaas a food reward. After experiencing this association, preferences toward MeSA were assessed.

We found that field-collected males showed orientation to odors released by caterpillar-damaged plants, but naïve lab-reared individuals showed no preference. When conditioned females were tested in the field, they chose M. sexta damaged plants. Similarly, nymphs conditioned to MeSA showed an orientation response to this HIPV. Unexpectedly, adults did not display a distinct preference upon conditioning. These results suggest that sting bug attraction to volatile cues is acquired by learning rather than innate. We have learned not only that associative learning is the mechanism underling this interaction, but also that this predator can be conditioned to specific HIPVs, components of a more complex odor blend