Fig 1.
The life-cycle of the strepsipteran Xenos vesparum in parallel with the life-cycle of its primary host, the paper wasp Polistes dominula.
a) X. vesparum female. An extragenital canal opens in the cephalothorax of the female, where both mating and larval escape occur. b) Triungulins escaping from female canal. c) Parasitized workers on C. radicans. Note the distortion of wasp abdomen due to parasites (arrows). d) X. vesparum male. Observe the striking sexual dimorphism of the parasite. e) A parasitized P. dominula male. f) Aggregation of parasitized wasps. Photos by Laura Beani.
Fig 2.
Sweep-netting collections of P. dominula wasps.
Collections were carried out on two C. radicans bushes (A and B) and one bush each of rose and jasmine (R and J) across 7 years (2009–2015). By clumping together 7 years of collections, the percentage of parasitized wasps out of all wasps was 68.7% on A, 65.6% on B, 5.9% on R and 6.1% on J. Timeline of experiments: * years of Mark-recapture (2011–2013); ^ year of Focal observations (2015); # year of Sweep-netting outside Sesto Fiorentino (2015).
Table 1.
Sweep-netting collections of P. dominula wasps from C. radicans bushes in 4 different locations in Tuscany (July 2015).
Parasitized wasps were more abundant than non-parasitized wasps in 10 out of 13 bushes.
Fig 3.
Mark-recapture of P. dominula wasps on bush A (2011–2013).
Spatial and feeding behavior. Parasitized workers spent a long time feeding on inflorescences, touching the surface with antennae and mandibles. Their activity was focused mainly on buds and calices, which were carefully patrolled (Fig 4).
Fig 4.
A parasitized wasp foraging on a closed bud of C. radicans.
Note two puparia of X. vesparum extruding from the host abdomen, one left open after the male’s emergence and the other still closed (arrows). Photo by Laura Beani. In the inset, flower buds with several extra-floral nectaries. Photo by Corrado Tani.
Fig 5.
Behavioral frequencies of focal parasitized (N = 10) and un-parasitized (N = 9) wasps on bush A (events /10-min, July 2015).
White box plots: un-parasitized wasps; grey box plots: parasitized wasps. Thick horizontal lines represent medians, boxes are upper and lower quartiles and whiskers indicate the highest and lowest values. (* P < 0.01).
Fig 6.
Scatterplot of the first two axes obtained by Principal Coordinates Analyses.
The two groups of wasps (white circles = un-parasitized, grey circles = parasitized) are almost perfectly separated along the first axis.