Debris-Carrying in Larval Chrysopidae: Unraveling Its Evolutionary History

Abstract

Abstract Larval debris-carrying, which occurs in many insect taxa, is a remarkable behavioral trait with substantial life history significance. For the Chrysopidae, information on the topic is scattered, and the habit's diversity and evolutionary history are unassessed. Here, we compile a comprehensive, annotated catalog on chrysopid debris-carrying and its associated larval morphology, and we identify emerging systematic patterns of variation, from larval nakedness to the construction of elaborate packets. Then, we examine these patterns in the context of available phylogenies with two objectives: 1) to begin unraveling the evolutionary history of chrysopid debris-carrying and 2) to evaluate the current and potential role of larval morphology (including debris-carrying modifications) in classification and phylogeny of this family. Debris-carrying: the literature revealed that debris-carrying occurs in the chrysopoid fossil record and in all three extant chrysopid subfamilies, including those proposed as basal (Nothochrysinae, Apochrysinae). Nevertheless, the family's ancestral state remains unresolved. The habit may have evolved at least once in Nothochrysinae or been lost several times. Larvae from only one genus of Apochrysinae are known, and they are debris-carriers. Each of the four tribes of the third subfamily, Chrysopinae, has distinctive debris-carrying characteristics. In ankylopterygine larvae, debris-carrying modifications seem relatively conserved. Among the ant-associated belonopterygine genera, debris-carrying is either highly evolved or, in one case, possibly absent. Within the large chrysopine tribe, nakedness and debris-carrying appear to have evolved independently numerous times; also, some reversals may have occurred. With one possible exception, leucochrysine genera have debris-carrying larvae. Larval morphology: scrutiny of the literature showed that all chrysopid genera whose larvae are known exhibit characteristic suites of anatomical structures related to carrying debris. Moreover, larval morphology provides strong (synapomorphic) evidence for the monophyly of four of the seven suprageneric chrysopid taxa: the subfamily Nothochrysinae and three of the four tribes of Chrysopinae (Ankylopterygini, Belonopterygini, and Leucochrysini). Larval morphological and debris-carrying characteristics appear to support some, but not all, previously proposed generic relationships within the tribe Chrysopini. Given the demonstrated potential advantages for including larval characters in chrysopid phylogenetic studies, it is essential to enhance the pool of available larval data. Therefore, we propose that citizen-scientists be involved in gathering verifiable data and that systematists develop comprehensive data matrices for comparative larval studies.