Larval head morphology of Phycosecis litoralis (Pascoe) (Coleoptera : Phycosecidae) with phylogenetic implications

Abstract

The larval head of a Phycosecis species is described and illustrated. Characters are compared to those found in larvae of other groups of Cucujiformia. Monophyly of all cleroid families examined is supported by several apomorphic features at least partly correlated with predacious habits: antennae directed anteriad, absence of the mandibular mola, presence of a pedunculate seta on the mala, presence of a median endocarina, origin of antennal muscles exclusively from the head capsule, and presence of a weakly pigmented, parallel-sided gular plate. A possible apomorphy of Cleroidea excluding Phloiophilidae is the parallel-sided, prognathous head. A sister-group relationship between Phycosecidae and Melyridae is supported by the presence of a plumose lacinia mobilis and secondary loss of the median endocarina. A monophylum comprising Cleridae + Chaetosomatidae is characterised by a strongly elongated, sclerotised larval gula, the strongly protracted position of the ventral mouthparts, and a cardo as long as or longer than the stipes. Monophyly of Trogossitidae is only weakly supported. Several apomorphies indicate a sister-group relationship between Cleroidea and Nitidulidae. These two taxa are characterised by a fully developed maxillolabial complex, an elongated prepharyngeal tube, and tergal sclerotisation restricted to the prothorax and tergite IX. A tentorial bridge completely separated from the remaining tentorium, and a maxillolabial complex with partly restricted motility of the maxilla are shared derived features of larvae of Cleroidea, Nitidulidae, Coccinellidae and Endomychidae. An unusual attachment of a part of the tentoriostipital muscle to the floor of the prepharyngeal tube is found in all cleroid and cucujoid larvae examined. Cleroidea are a well-defined monophyletic group and may form a monophylum together with a paraphyletic assemblage of Cucujoidea. A close relationship between Cleroidea and Lymexylidae is refuted.