Molecular and morphological characterization of third instar Palaearctic horse stomach bot fly larvae (Oestridae: Gasterophilinae, Gasterophilus).

Species of Gasterophilus are obligate parasites of equids and may induce severe, even lethal myiasis. However, identification of the third instar Gasterophilus larva at the species level is still problematic predominantly due to a shortage of diagnostic morphological features and incomplete molecular libraries. Testing the suitability of three different molecular markers showed that the traditional 650 bp barcode region near the 5' terminus of the cytochrome c oxidase subunit I (COI) served as a better tool for species-level identification than a 663 bp region near the 3' terminus of COI and a 554 bp region near the 5' terminus of the large subunit ribosomal RNA. We found that barcoding discriminates G. intestinalis, G. nasalis, G. nigricornis and G. pecorum but not G. haemorrhoidalis and G. inermis. A comparative morphological study using scanning electron microscopy was conducted to promote the identification of the third instar larvae. Photographs of fresh mature third instar larvae are provided for all species, and the remarkable green body colour of third instar G. nigricornis is fully documented for the first time. Two morphological keys are provided, one is suitable for quick identification, and the other based on ultrastructural details is provided for further comparative morphological investigation. A new term 'oral plate' instead of 'mandible' was proposed for a pair of sclerites of uncertain homology emerging from the secondary mouth opening. Our data shows that DNA barcodes cannot replace morphology for identification of third instars of Gasterophilus species, and a scaffold is provided for an integrated taxonomic reference system, which will contribute to monitoring gasterophilosis for equid welfare and protection, and also facilitate further studies in functional anatomy, phylogenetic analyses and host-parasite co-evolutionary investigations of Gasterophilus.

Fine structure of Delia platura (Meigen) (Diptera: Anthomyiidae) revealed by scanning electron microscopy.

Delia platura (Meigen) is a phytophagous fly that can cause significant crop losses. To obtain a better understanding of the external morphology of this species, adult D. platura is studied using scanning electron microscopy. Organs or structures that are important for taxonomy, such as the compound eyes, spiracles, pulvilli, wings, and genitalia are highlighted to complement previous description based on light microscope. Mesothoracic and metathoracic spiracles of D. platura that provide efficiency in preventing entrance of fine materials or dust into the tracheal system are morphologically different. In addition, the elongate-oval pulvillus is densely covered with tenent setae with spoon-like tip, which can increase the number of contact points for attachment to a surface. Four types of sensilla are observed on the male genitalia of D. platura including: trichoid sensilla, chaetic sensilla, three subtypes of campaniform sensilla, and basiconic sensilla. Long bristles and microtrichiae are observed on the female genitalia of D. platura. The possible function of sensilla located in the genitalia of D. platura is discussed. Microsc. Res. Tech. 77:619-630, 2014. © 2014 Wiley Periodicals, Inc.

Ultrastructure of antennal sensilla in Hydrotaea armipes (Fallén) (Diptera: Muscidae): new evidence for taxonomy of the genus Hydrotaea.

The morphology and ultrastructure of the antennal sensilla of male Hydrotaea (Hydrotaea) armipes (Fallén) are examined via scanning electron microscopy in order to highlight the importance of antennal sensilla as a source of morphological characters for taxonomy and phylogeny of Hydrotaea. Antennal scape and pedicel have only one type of sensilla, the sharp-tipped chaetic sensilla, whereas antennal funiculus possesses several types of sensilla, including trichoid sensilla, two subtypes of basiconic sensilla, coeloconic sensilla and clavate sensilla. These results are compared with previously published studies on other fly species, especially on H. (H.) irritans (Fallén) and H. (Ophyra) chalcogaster (Wiedemann), and there are possible uniquely derived characters or diagnostic characters examined on antennal pedicel and antennal funiculus, which suggests either affinities and divergence between species at subgenus level. Thus, new morphological evidence is provided, which might help to develop the much disputed taxonomy of genus Hydrotaea Robineau-Desvoidy in future.

Sensilla on antenna and maxillary palp of predaceous fly, Lispe neimongola Tian et Ma (Diptera: Muscidae).

This study describes aspects of sensilla on the antennae and maxillary palps of an aquatic predator, Lispe neimongola Tian et Ma. Types, distribution and density of sensilla were studied by stereoscopic microscope and scanning electron microscopy. The antennal scape has one type of sensilla, the sharp-tipped chaetic sensilla; whereas, the antennal pedicel possesses two subtypes of these sensilla. Three types of sensilla are found on antennal funiculus: trichoid sensilla, basiconic sensilla (two subtypes) and clavate sensilla. Sensilla found on palpal surface include the third subtype of basiconic sensilla and chaetic sensilla. Two unique sensillar characters of L. neimongola detected are the absence of coeloconic sensilla on antennal funiculus and the greater number of basiconic sensilla on spoon-like palps. These results are compared with equivalent findings in several other Calyptratae fly species of different ecotypes to provide evidence of adaptation to their environment.

Cuticular structures on antennae of the bot fly, Portschinskia magnifica (Diptera: Oestridae).

Portschinskia magnifica Pleske, 1926, is an endangered subcutaneous parasitic fly of voles that mimics bumblebees in appearance. Although the importance of antennae in Diptera has been repeatedly stressed, there is still a lack of morphology information of this group, let alone this species. Antennae of adult P. magnifica were studied with a stereoscopic microscope and scanning electron microscope. Six subtypes of antennal sensilla were observed on the funiculus and arista (one subtype of trichoid sensilla, one subtype of basiconic sensilla, and four subtypes of coeloconic sensilla). Sensilla on the antennal funiculus from one sample of both male and female flies were also mapped. Female P. magnifica bear a larger number of sensilla than males, and more sensilla were discovered on the posterior surface than on the anterior surface. However, what make this species special are the distinct structures and new morphological characteristics discovered in the antenna. The antennal funiculus of P. magnifica is completely enveloped by an antennal pedicel. A large number of branched or unbranched trichoid and basiconic sensilla are identified on the antennal funiculus. These two make the most numerous types of sensilla distributed all over the funicular surface. P. magnifica has the most coeloconic sensilla subtypes in previously studied oestrid flies. A total of four subtypes of coeloconic sensilla are found, with subtype I and subtype II on the proximal and middle part of the antennal funiculus and subtype III and subtype IV on the antennal arista. Two large bristles that resemble mechanoreceptors on the proximal two antennal segments located close to the arista are a unique feature. This has never been described in the oestrid funiculus. Interestingly, these bristles can appear as multi-tipped short structures in some individuals. P. magnifica lacks sensory pits that are usually abundant in other oestrid flies. The size, number, and distribution of sensilla on the male and female antennal funiculus are provided here, armed with a discussion of their presumable sensilla functions and evolutionary trends.

Olfactory sensilla on antennae and maxillary palps of Fannia hirticeps (Stein, 1892) (Diptera: Fanniidae).

The Fanniidae is one of four families in the superfamily Muscoidea (Diptera), including some important medical and hygienic flies. There is a paucity of reports on the ultrastructure of olfactory sensilla for the fanniid species. To provide more information on the morphology of the antennal and palpal sensilla of fanniid fly, Fannia hirticeps (Stein, 1892) has been studied using scanning electron microscopy. The first two antennal segments, scape and pedicel, are covered by microtrichiae and several chaetic sensilla. Six distinct morphological types of sensilla are recorded on the antennal funiculus, including one trichoid, two basiconic, two coeloconic sensilla, and one clavate sensilla. The measurement and density of each sensilla type are also provided. The trichoid sensilla tend to be longer and denser toward the apex of antennal funiculus. Basiconic sensilla spread all over the funicular surface. F. hirticeps bears two types of coeloconic sensilla, type 2 coeloconic sensilla distributed on the distal part of the anterior surface, whereas type 1 distributed on the rest of the funiculus. Clavate sensilla are found on the base of antennal funiculus. Only one large sensory pit is located on the posterior surface. Maxillary palps bear one type of basiconic sensilla. These results are compared with eight other muscid flies. Our findings provide a morphological basis for future investigations on olfactory-mediated behavior of this group.