The meadow spittlebug Philaenus spumarius L. (Hemiptera: Aphrophoridae) is a
xylem-sap
feeder and the most abundant and widespread vector of Xylella fastidiosa
(Xanthomonadales: Xanthomonadaceae) throughout Europe. Control strategies
for the disease are based on containment and eradication measures regulated by the
European Union. Within the context of biological control, the use of natural enemies
aims at limiting the insect vector population in agroecosystems. Spiders are generalist
predators with potential as biological control agents occupying all the habitats within
crops. Crab spiders (Thomisidae) could be potential natural enemies against P. spumarius.
The functional response (FR) of a predator represents the intake rate as a function
of food availability and allows estimating feeding behaviour parameters such as the
prey handling time and attack rate. However, spiders often kill more prey than they
consume, unveiling their capacity as natural enemies. We assessed and compared the
FR of Xysticus acerbus (Thomisidae) fed on P. spumarius in the laboratory considering
(1) the total number of dead individuals and (2) only the consumed ones. We found
that although both FRs were of type-II,
they significantly differed. The values of attack
rate and handling time for consumed were 0.1 and 3.6, respectively, while for
dead, the attack rate was 0.3 and 1.1, being both significantly different. Moreover,
the number of overkilled individuals reached a plateau at the highest prey densities.
Xysticus acerbus could be a potential natural enemy of P. spumarius. Nevertheless, we
suggest that the effect of including the killed but not consumed prey individuals in
FR studies using wasteful killing predators should be considered and further studied.
