Platycampus larvae are highly cryptic leaf feeders characterised by a dorso-ventrally flattened body, the dorsal integument resembling a shield. Dorsal and ventral cuticles from Platycampus luridiventris were compared by histology and gel electrophoresis. By Azan-staining, a red and a blue layer were distinguished in the dorsal cuticle, while the ventral cuticle showed one, almost uniform blue layer, as in both cuticles of control species. The two cuticles from P. luridiventris had similar amounts and sodium dodecyl sulphate-polyacrylamide gel electrophoresis profiles of soluble proteins, but not insoluble proteins. One insoluble protein (MW approximately 41 kDa) was visible as a large band in the ventral cuticle only. It is likely that this protein renders the cuticle elastic, and that the dorsal, red layer is the exocuticle, mainly composed of insoluble proteins. We discuss eco-physiological implications of the exocuticle in insects. Further, data from the literature indicate that the defence strategy in P. luridiventris larvae relies on being visually cryptic towards avian predators and tactically cryptic towards arthropod predators and parasitoids. Crypsis in both senses is favoured by the shield effect, itself based on an abnormally thick dorsal exocuticle. Although the larvae are external feeders, they may be considered as hidden from an ecological perspective.
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‘Arctocyonids’ are generally considered as including some of the most primitive ‘ungulates’ from the Paleocene. Although more than 15 genera are known from North America, European members of this order are less common and mainly belong to derived genera such as Arctocyon. However, one species of primitive arctocyonid, Prolatidens waudruae, was described from the early Paleocene of Hainin, Mons Basin, Belgium. Here we describe new dental positions of this small taxon, including for the first time upper molars and upper fourth premolar. Morphological comparisons confirm the position of P. waudruae among primitive ‘ungulates,’ with the closest North American arctocyonids being Prothryptacodon furens and Oxyprimus galadrielae. Oxyprimus galadrielae features slightly more primitive morphological traits than both other species. Apheliscids share several characters with Prolatidens, but the latter lacks the apomorphies defining the family. Among ‘arctocyonids,’ Prolatidens shares with only Protungulatum and Oxyprimus the incomplete lingual cingulum at the base of the protocone of M1. Prolatidens waudruae is unique among Procreodi in its combination of primitive and derived characters. The cladistic analysis places P. waudruae close to the base of the ingroup, indicating that this species is among the most primitive members of the Paleocene ‘ungulates.’ However, the lower nodes of the trees are not well supported and definitive conclusions should await more complete specimens and analysis. Apheliscids are situated relatively far from Prolatidens, suggesting that the resemblances between them are better considered as convergences. Based on the morphological comparisons, the arctocyonid from Hainin correlates best with North American Torrejonian taxa.
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