Comparative study of sensilla and other tegumentary structures of Myrmeleontidae larvae (Insecta, Neuroptera)

Abstract

Antlion larvae have a complex tegumentary sensorial equipment. The sensilla and other kinds of larval tegumentary structures have been studied in 29 species of 18 genera within family Myrmeleontidae, all of them with certain degree of psammophilous lifestyle. The adaptations for such lifestyle are probably related to the evolutionary success of this lineage within Neuroptera. We identified eight types of sensory structures, six types of sensilla (excluding typical long bristles) and two other specialized tegumentary structures. Both sensilla and other types of structures that have been observed using scanning electron microscopy show similar patterns in terms of occurrence and density in all the studied species (with few exceptions). The sensilla identified are: coeloconica, placoidea, basiconica, trichodea type I, trichodea type II, and campaniformia. All these sensilla have mechano‐ or chemosensorial functions. Some regions of the larval body have been studied using SEM for the first time, such as the surface of the food canal, which bears sensilla coeloconica, and the abdominal segment X, that bears three types of sensilla: coeloconica, basiconica, and campaniformia. Sensilla placodea are newly reported on antlion larvae, being present on the mandibular base, pronotum, mentum, and cardum. Also, new locations of sensilla coeloconica (e.g., on rastra) and sensilla campaniformia (e.g., on odontoid processes) are noted. A novel porous texture with chemoreceptor function has been identified in the base of mandibles. A mechanism of dentate‐notched surfaces that anchor maxillae and mandible, reinforcing the food canal, is detailed. All these sensorial structures, in addition to ocular tubercles for light caption and their great muscular system, confer to these larvae an extraordinary predation capacity to success hunting and living in such harsh environments.

Setae and sensilla in the Iberian Myrmeleon Linnaeus, 1767 larvae (Insecta, Neuroptera: Myrmeleontidae)

“…All species studied are recognizable using external morphological characters such as size, coloration, and distribution and abundance of bristles of the mandible external to maxilla and digging setae (Badano and Pantaleoni, 2014a;Badano et al, 2016). However, all Iberian Myrmeleon species of this study present the same types and shape of bristles, plumose hairs, digging setae and the rest of sensilla, as we supposed with some previous studies (Lipovšek Delakorda et al, 2009;Pantaleoni et al, 2010;Devetak et al, 2010a;Ngamo and Maoge, 2014;Acevedo Ramos et al, 2020). All types of sensilla found on previously studied antlion larvae were observed in Iberian Myrmeleon larvae except digitiform sensilla found in M. formicarius (Lipovšek Delakorda et al, 2009) and Myrmecaelurus trigrammus (Devetak et al, 2013), both species with pit-building behavior.…”

“…All types of sensilla found on previously studied antlion larvae were observed in Iberian Myrmeleon larvae except digitiform sensilla found in M. formicarius (Lipovšek Delakorda et al, 2009) and Myrmecaelurus trigrammus (Devetak et al, 2013), both species with pit-building behavior. Sensilla basiconica were not observed on X abdominal segment, as were found in Synclisis baetica and Macronemurus appendiculatus (Acevedo Ramos et al, 2020).…”

“…According to their functions, bristles, plumose hairs and digging setae have a mechanosensorial role (Lipovšek Delakorda et al, 2009;Acevedo Ramos et al, 2020). Also, bristles (especially those located on head capsule and mandibles) are used to throw away sand during the construction of pitfall traps and to throw it to their preys, plumose hairs are used to retain soil particles in their body in a camouflage role, and digging setae allow to bury themselves (Lipovšek Delakorda et al, 2009;Devetak et al, 2013;Badano and Pantaleoni, 2014a;Acevedo Ramos et al, 2020). It is remarkable the absence of dolichasters, as on other genera that construct pitfall traps as Myrmecaelurus or Euroleon (Nicoli Aldini, 2007;Lipovšek Delakorda et al, 2009;Devetak et al, 2013;Badano and Pantaleoni, 2014a).…”

“…The family Myrmeleontidae is the most diverse family within Neuroptera, probably due to the great adaptations of their larvae (Mansell, 1999;Pantaleoni, 2014a, 2014b;Acevedo Ramos et al, 2020). These larvae show a high diversity of lifestyles and types of habitats such as tree holes, burrows, caves, etc.…”

“…These larvae show a high diversity of lifestyles and types of habitats such as tree holes, burrows, caves, etc. ; nevertheless, the psammophilous adaptations of antlions probably reached the most successful lifestyle (Mansell, 1999;Stange, 2004;Pantaleoni, 2014a, 2014b;Acevedo Ramos et al, 2020).…”