Selected representatives of Cucujoidea, Cleroidea, Tenebrionoidea, Chrysomelidae, and Lymexylidae were examined. External and internal head structures of larvae of Sphindus americanus and Ericmodes spp. are described in detail. The data were analyzed cladistically. A sister group relationship between Sphindidae and Protocucujidae is suggested by the vertical position of the labrum. The monophyly of Cucujiformia is supported by the reduced dorsal and anterior tentorial arms, fusion of galea and lacinia, and the presence of tube-like salivary glands. Absence of M. tentoriopraementalis inferior and presence of a short prepharyngeal tube are potential synapomorphies of Cleroidea, Cucujoidea and Tenebrionoidea. The monophyly of Cleroidea and Cucujoidea is suggested by the unusual attachment of the M. tentoriostipitalis to the ventral side of the posterior hypopharynx. Cucujoidea are paraphyletic. The families Endomychidae, Coccinellidae and Nitidulidae are more closely related to the monophyletic Cleroidea, than to other cucujoid groups. Separation of the posterior tentorial arms from the tentorial bridge and presence of a maxillolabial complex are synapomorphic features of Cleroidea and these cucujoid families. For a reliable reconstruction of cucujoid interrelationships, further characters and taxa need to be studied.