# Sensillar Ultrastructure of the Antennae and Maxillary Palps of the Warble Fly Oestromyia leporina (Pallas, 1778) (Diptera: Oestridae)

## TL;DR

This study examines the ultrastructure of the antennae and maxillary palps of the warble fly Oestromyia leporina to identify potential evolutionary traits useful for taxonomy.

## Contribution

The study identifies new potential synapomorphies in Oestridae based on sensillar morphology and arista features.

## Key findings

- Oestromyia leporina has the most complex maxillary palps in Calyptratae.
- Three potential synapomorphies were identified in the arista of Oestridae species.
- Multiple types of sensilla were found on the antennae and maxillary palps.

## Abstract

Few synapomorphy is available in the important parasitic family Oestridae to clarify its phylogenetic relationships. We used scanning electron microscopy to investigate the morphological structure and ultrastructure of antennae and maxillary palps of male Oestromyia leporina, describing the sensillar morphology, types, and distribution. Interestingly, this species has the most complex maxillary palps that are known in Calyptratae. We then proposed that the possible synapomorphy in features of antennal arista by comparing between all published Oestridae species. This study indicates the value of the morphology of antennae and maxillary palps in taxonomy studies in Oestridae and calls for more in-depth studies.

Despite the development of molecular techniques, morphological phylogeny still remains integral in underpinning the relationship between some clades of Calyptratae, especially the ones with fast radiation, such as those in Oestridae (Diptera: Brachycera), yet few synapomorphy has been proposed for adults in this family. Using scanning electron microscopy, we investigated the morphological structure and ultrastructure of the antennae and maxillary palps of adult Oestromyia leporina (Hypodermatinae, Oestridae). One type of trichoid sensillum (Tr), three types of basiconic sensilla (Ba I, Ba II, and Ba III), one type of coeloconic sensillum (Co I), and one type of clavate sensillum (Cl) were found on the antennal postpedicel. Surprisingly, this species has the most complex types of sensilla on the maxillary palps that have been reported in Calyptratae so far, with two types of coeloconic sensilla (Co II and Co III) and two types of mechanoreceptors. We then identified three common characteristics on the arista of Oestridae (Hypodermatinae, Oestrinae, Gasterophilinae and Cuterebrinae) that are potential synapomorphies. These characteristics indicate the value of the morphology of maxillary palps and aristae in taxonomy studies of Calyptratae.