The larval morphology of the clonal raider ant, Ooceraea biroi (Forel, 1907) (Dorylinae), with broader implications for the Formicidae and Hymenoptera

The larvae of ants are essential for colony organization and growth, yet knowledge of their internal anatomy is sparse, and the homologies of many larval structures remain uncertain. We therefore used synchrotron-radiation micro-computed tomography (SR-μ-CT) and scanning electron microscopy (SEM) to investigate, respectively, the internal and external morphology of the larva of the clonal raider ant, Ooceraea biroi (Forel, 1907), a model species for experimental biology. The documented characters are compared with conditions found in other Formicidae and Hymenoptera, and more broadly with features of larvae of other orders of Holometabola. As in other groups of Aculeata (and Orussidae), the body of Ooceraea is grub-like and depigmented, with distinctly reduced cephalic structures, and a weakly sclerotized, strongly simplified, sausage-like postcephalic body. This larval pattern reflects a distinct simplification compared with immature stages in the symphytan grade, with completely reduced eyes, antennae, and extrinsic labral muscles, vestigial palps, and missing thoracic legs and abdominal prolegs. Despite a simplified and largely uniform body configuration in apocritan larvae, including ants, there is considerable variation. ... mehrLarvae of Formicidae vary distinctly in external features, especially in the general body shape, setation, and mandibular teeth. We therefore summarize eight morphological characters from previous studies to contextualize our findings, highlighting the often-underestimated diversity of larval morphology, which provides fertile ground for future study. Our study extends the knowledge of the external and internal morphology of ant larvae by taking a multi-modal approach to phenotype sampling, particularly via μ-CT. These methods have the potential of rapidly increasing the knowledge of previously neglected larval morphology, facilitating deeper investigations of evolutionary transformations in immature stages and providing a more complete picture of the evolution of an ecologically paramount group of insects.