Results
Larders contained mostly invertebrates (Table 2). Hymenoptera accounted for 87.4% of impaled prey, of which the common bumblebee, Bombus terrestris , was by far the favourite prey item accounting for 85.4% of all Hymenoptera. The second most frequent prey group were Orthoptera (7.4%), consisting of large specimens, with the migratory locustLocusta migratoria t he most commonly found species (3.7%). Beetles were the third most frequent prey group accounting for 3.4% of all prey collected. These are also large subjects and includedCarabus coriaceus coprophage and Scarabaeidae such as Bubas bubalus . We also found some vertebrates (0.6%) such as the wood mouseApodemus sylvaticus and the white-toothed shrew Crocidura russula , which are particularly important for fresh biomass. Other marginal prey included the earthworm Lumbricus terrestris(1.2%).
Among the Hymenoptera prey observed on the larders (Figure 2) were invasive and aggressive yellow-legged hornet ,Vespa velutina , which was likely speared for detoxification.
There were also some large orthoptera with broad wings and jagged legs and Coleopterae with strong shells and chemical defences. The devil’s coach beetle, Ocypus olens , in particular, is known for raising its long and uncovered abdomen and opening its jaws like a scorpion when threatened. Though it does not have a stinger, it can deliver a painful bite with its strong, pincer-like jaws. It also gives off a foul-smelling odour that stems from a defensive liquid secreted by two white glands at the end of its abdomen.
We also found the praying mantid ,Mantis religiosa, among the prey items. They possess a raptorial foreleg with unusually long coxa, which, together with the trochanter, give the impression of a femur. The femur itself is the proximal segment of the grasping portion of the leg.
Measurements of the bristles and beaks on museum specimens yielded the following mean lengths (± one standard deviation) (Figure 4):
Bristles: 10.27±0.12 mm
Beak 15.96±0.21 mm
The high-resolution digital photographs clearly show a row of feathers above the eyes (Figure 5). These coverts form a dense network of barbels pointing upwards, like a thick eyebrow. In the loral area, between the eye and the beak, there are feathers with black rachis and vanes ending with an open pennaceous portion with vertical barbs (Figure 6). Furthermore, there is a cluster of four strong rictal bristles with bare shafts at the commissure of the mandibles on the upper maxilla, thick, curved down, and protruding from the lower mandible (Figure 6).
In addition, a series of smaller bare shaft bristles occupy the loral region at the base of the culmen, covering a narrow band of the upper part of the mandible (Figure 6).
During these photographic sessions, we noticed a different type of behaviour related to the protection of the beak area, namely the cleaning of residual dirt by rotating the head very quickly (Figure 7).