ASILOIDEA, Latreille, 1802

Grimaldi, David A., 2016, Diverse Orthorrhaphan Flies (Insecta: Diptera: Brachycera) In Amber From The Cretaceous Of Myanmar: Brachycera In Cretaceous Amber, Part Vii David A. Grimaldi, Bulletin of the American Museum of Natural History 2016 (408), pp. 1-132 : 62-63

SUPERFAMILY ASILOIDEA

This group contains approximately 8100 described species in eight or nine living families. The position of the small Holarctic family Hilarimorphidae has been ambiguous ( Trautwein et al., 2010), including it being the sister group to the Bombyliidae ( Woodley, 1989; Yeates, 1994), or to the Eremoneura ( Yeates, 2002). The proposal that Hilarimorphidae is a sister group to the Acroceridae ( Wiegmann et al., 2011) is morphologically anomalous, possibly a result of these two being basal families. Other than Hilarimorphidae , which is a cool temperate group, Asiloidea are by far most diverse and abundant in xeric regions, from deserts and chaparral to Mediterraean biomes, where they are important pollinators. Anthophilous species with long mouthparts occur in Bombyliidae , Mydidae , Apioceridae , and Scenopinidae .

The consensus on asiloid relationships is the following: Hilarimorphidae + Bombyliidae ; Asilidae + Mydidae + Apioceridae ( Woodley, 1989; Yeates and Irwin, 1996; Dikow, 2009; Yeates, 2002; Wiegmann et al., 2011); and the “therevoid” clade, comprised of Apsilocephalidae + Evocoidae + Therevidae + Scenopinidae ( Yeates, 2002; Wiegmann et al., 2011; Winterton and Ware, 2015). The earliest definitive fossils of asiloids occur in the Cretaceous, with Asilidae and Mydidae in the Aptian-aged Crato limestone of Brazil (Grimaldi, 1990; Wilkommen and Grimaldi, 2007); additional Asilidae occur in Burmese and New Jersey amber (Dikow and Grimaldi, 2014). Apsilocephalidae and Bombyliidae occur in Burmese amber (Gaimari and Mostovski, 2000; Grimaldi et al., 2011; herein), and a putative Scenopinidae was reported in New Jersey amber ( Grimaldi and Cumming, 1999), but which needs to be restudied. Evocoidae have no fossil record (but see below, under Burmapsilocephala , n. sp.), and definitive fossil Therevidae are only Tertiary ( Metz and Irwin, 2000; Hauser and Irwin, 2005). Most asiloid families are well represented as lithified remains and amber inclusions from the Tertiary (Evenhuis, 1994).

A small, long-proboscid fly in Early Cretaceous Lebanese amber, Cretahilarimorpha Myskowiak et al. has been assigned to Hilarimorphidae ( Myskowiak et al., 2016) . This is a very unusual fly. On the one hand, its venation is easily derivable from extant Hilarimorphidae , with long br-bm cells, no discal cell, and a short, asymmetrical R 4 -R 5 fork. Vein R 2+3 is very short, nearly meeting the apex of R 1, which makes the venation also resemble that of Chimeromyiidae , a small family of tiny flies in Cretaceous amber ( Grimaldi et al., 2009). Chimeromyiidae , however, are eremoneurans, and Cretahilarimorpha is far more basal. Unlike Hilarimorpha , Cretahilarimorpha has a short costal vein, as in Stratiomyidae , but the most significant structure is the antenna. The antenna in the fossil is robust, with eight large, tapering flagellomeres, as seen in stratiomyomorphans and tabanomorphans. I am unaware of any Muscomorpha, including Asiloidea and Nemestrinoidea , that has such a primitive antennal structure. Hilarimorphid antennae are short, with three flagellomeres (the apical two forming a small, thin, styluslike portion). The empodium of Cretahilarimorpha is apparently reduced ( Myskowiak et al., 2016), but it is uncertain whether it is setiform. The long, projecting proboscis is autapomorphic and not revealing of relationships. Given this situation, I am hesitant to include Cretahilarimorpha in Asiloidea or Muscomorpha.

Molecular models and biogeography support a Late Mesozoic diversification of asiloids. Basal, subfamily-level divergences of Therevidae and Scenopinidae are estimated to be Cretaceous (Winteron et al., 2015; Winterton and Ware, 2015). A relatively derived phylogenetic position of Burmapogon in Burmese amber (Dikow and Grimaldi, 2014) indicates that basal divergences of Asilidae must extend at least to the Early Cretaceous, perhaps Late Jurassic. The relationships of the subgenera of Apiocera and genera of megasceline Mydidae are biogeographically congruent: western North America ( South Africa ( Australia + southern South America)) ( Yeates and Irwin, 1996). Interestingly, the Apsilocephalidae and Evocoidae , which are likely sister groups, share a similar disjunct distribution (but not including Africa). The Apiocera and mydid taxon-area relationships were interpreted as Pangean in origin, 160–180 Ma ( Yeates and Irwin, 1996), which I consider as probably too old, but a topic that lends additional significance to the asiloids in Burmese amber.

Comments on the small crossvein sc-r are worthwhile here, particularly since the vein is present in many of the fossil bombyliids described below. Crossvein sc-r is widespread in Asilidae and occurs in many Bombyliidae (e.g., Apolysis , Crocidium , Paracosmus , Phthiria , etc.), some Nemestrinidae (e.g., Neorhynchocephalus ), in the Mesozoic family Eremochaetidae (Grimaldi and Barden, 2016) , and Evocoidae . It is widespread in the Syrphidae , though not in the Pipunculidae or aschizan Cyclorrhapha. It could be argued that the crossvein is developed multiple times in assorted lineages (e.g., associated with hovering flight), but it may be diagnostic for the Muscomorpha and lost multiple times in more derived groups.