Asiobaccha Violovitsh, 1976

Mengual, Ximo, 2016, A taxonomic revision of the genus Asiobaccha Violovitsh (Diptera: Syrphidae), Journal of Natural History 50, pp. 2585-2645 : 2587-2590

Genus Asiobaccha Violovitsh, 1976

Type species Baccha nubilipennis Austen, 1893

Differential diagnosis

Medium to large species, slender with petiolate abdomen. Face straight with a distinct tubercle; oral opening elongated; antenna short, shorter than face, with basoflagellomere longer than broad ( Figure 1 ); antennal pits distinctly separated; eye bare; male holoptic; ocellar triangle narrow. Scutum with or without mesonotal fringe; postpronotum bare; scutellum with or without subscutellar fringe, without bristles. Proepimeron bare; anterior anepisternum pilose on posterodorsal part or dosomedially; metasternum bare; metaepisternum pilose ventrad to spiracle; postmetacoxal bridge incomplete ( Figure 1 ). Wing with or without alula, with black minute sclerotised dots on posterior wing margin; usually extensively microtrichose, never completely bare. Abdomen petiolate, unmargined; male genitalia small (except in Asiobaccha taronja sp. nov.) with a segmented aedeagus.

Geographical distribution

Asiobaccha species are distributed in the Oriental, Australian and Oceanian Zoogeographic Regions, extending into the Sino-Japanese Region sensu Holt et al. (2013). The species with the largest distribution is Asiobaccha nubilipennis , which occurs from Sri Lanka and India northwards to China and Japan, and south to Indonesia (Sumatra, Java, Sulawesi). However, the genus Asiobaccha is present farther south to Australia and New Caledonia, and eastwards to Fiji, Tonga, Tuvalu and Samoa, including New Guinea and Solomon Islands ( Figure 2 ). The highest diversity of the genus occurs in two classic biogeographical designations, Wallacea and Melanesia.

Natural history

Although nothing has been published about the biology of the adults, the author assumes that imagoes of Asiobaccha feed on pollen and nectar like many other syrphid adults, a fact corroborated by field observations (J. Skevington and A. Young, personal comments).

Very little is known about the immature stages of Asiobaccha . Muraleedharan and Radhakrishnan (1986) reported larvae of A. nubilipennis feeding on Aphis (Toxoptera) aurantii Boyer de Fonscolombe, 1841 ( Hemiptera : Aphididae ) in tea plantations in Anamallai Hills, India. Additionally, Radhakrishnan and Muraleedharan (1993) gave more details of the immature biology of A. nubilipennis , such as aphid consumption and larval stages duration, reared from A. aurantii from southern India. In New South Wales ( Australia), Carver et al. (2003) found a second-instar larva of Asiobaccha notofasciata sp. nov. feeding on Aphis (Aphis) clerodendri Matsumura, 1917 ( Hemiptera : Aphididae ) in a pseudogall of Clerodendrum tomentosum (Vent.) R.Br.

Systematics

Violovitsh (1976) and Curran (1928) described Asiobaccha and Allobaccha as subgenera of Baccha respectively, but only Baccha sensu stricto belongs to the tribe Bacchini ( Mengual et al. 2008; Mengual 2015). Based on recent molecular analyses ( Mengual 2015), the aforementioned three taxa are not related phylogenetically as suggested earlier and Asiobaccha and Allobaccha are related with other Syrphini genera ( Vockeroth 1969; Thompson and Rotheray 1998; Ichige 2009). Each of these three taxa belongs to a separate evolutionary lineage within Syrphinae , and Asiobaccha is close to Episyrphus and Meliscaeva . Mengual (2015) recognised Asiobaccha as a valid genus based on morphological characters and the molecular analyses performed.

Remarks

A total of 19 species are recognised in this revisionary work, with 10 species new to science described here. There are species with more morphological affinities to others that may form species groups, for example A. albipeza sp. nov., A. selsi sp. nov., A. praefica and A. samoaensis sp. nov. with black abdomens; species related to A. nubilipennis with a mesonotal fringe, such as A. aea sp. nov., A. virtuosa , A. doesburgi sp. nov., A. aquila sp. nov. and A. bimaculata ( Keiser, 1952) ; or species with the same abdominal pattern and without mesonotal fringe, such as A. loriae , A. tripartita and A. bicolor . None of these groupings deserves a supraspecific category. On the other hand, male genitalia among Asiobaccha species show subtle differences, except for A. taronja with very large male genitalia and modified sterna ( Figure 13a – d ).

Figures

Figure 1. Asiobaccha marissae Mengual sp. nov., lateral view. (a) Detail of the pilose posterior anepisternum; (b) detail of the pilose metaepisternum ventrad to spiracle.

Figure 2. World distribution of Asiobaccha Violovitsh. The limit shown is only an approximation defined by collecting points for specimens examined and literature records.

Figure 13. Asiobaccha nubilipennis (Austen). a–b, ♂, male genitalia. (a) Lateral view; (b) ventral view. Asiobaccha taronja Mengual sp. nov. c–d, paratype ♂, male genitalia. (c) Lateral view; (d) ventral view. Scale bars = 0.5 mm.