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The larval stage remains unknown for many sawflies, making it difficult to explore the phylogenetic significance of larval morphology. Here, we assemble a data set from the larval anatomy of 22 genera of Argidae and Zenargidae. We scored 85 characters for 48 terminal taxa and use a maximum parsimony approach applying equal (EW) and implied weights (IW) for phylogenetic reconstruction. We describe in detail for the first time the final larval instar of Zenarge turneri to illustrate the character systems employed. We retrieve the topology Zenarge + (Argidae s. stricto + Pergidae) in both EW and IW analyses; however, the branch support is low. We explore the phylogenetic relationships and character optimization based on the k value = 15 IW tree. Argidae s. stricto and Pergidae are recovered only under IW analyses. Within Argidae, two main clades are retrieved; these are congruent with the subfamilies Arginae and Sterictiphorinae s. Benson (1963). The genera Arge and Didymia are not retrieved as monophyletic. In general, the relationships produced by analyzing the larval morphology are consistent with those derived from adult morphology. We identify some patterns in the evolution of larval morphology of the Argidae. [ABSTRACT FROM AUTHOR]

Phytophagous insects tend to be either cryptic and solitary, or brightly colored and gregarious, as a defense against vertebrate predators. Here, we tested whether potent defensive chemicals produced de novo by larvae of Argidae and Pergidae sawflies have influenced the evolutionary relationship between larval appearance and levels of gregariousness. Phylogeny-based correlation analyses indicated only a weak trend for solitary species to be cryptic, and for gregarious ones to be conspicuous. Numerous Argidae were cryptic-solitary or conspicuous-gregarious, whereas most Pergidae were conspicuous-gregarious. Both families also included not truly gregarious but aggregated species, i.e. with individuals more evenly distributed on the host plant. By considering two specific morphological traits, predominant body coloration and contrasting spots on body, each one was (weakly) associated with appearance but none with gregariousness, which reflects the functional relevance of appearance as a whole. Furthermore, Argidae can display alternate appearances during successive larval instars. Finally, an independent contrasts test showed no obvious correlation between two major toxic peptides. Our results point towards diversely combined patterns of linked ecological traits in these insects. By assuming that warning coloration is more warranted against vertebrate than invertebrate predators, we suggest that the occurrence itself of toxins allowed this diversity via differing predator guilds and environmental factors, to which these insects were confronted during evolution. [ABSTRACT FROM AUTHOR]