Flies are one of four superradiations of insects (along with beetles, wasps, and moths) that account for the majority of animal life on Earth. Diptera includes species known for their ubiquity (Musca domestica house fly), their role as pests (Anopheles gambiae malaria mosquito), and their value as model organisms across the biological sciences (Drosophila melanogaster). A resolved phylogeny for flies provides a framework for genomic, developmental, and evolutionary studies by facilitating comparisons across model organisms, yet recent research has suggested that fly relationships have been obscured by multiple episodes of rapid diversification. We provide a phylogenomic estimate of fly relationships based on molecules and morphology from 149 of 157 families, including 30 kb from 14 nuclear loci and complete mitochondrial genomes combined with 371 morphological characters. Multiple analyses show support for traditional groups (Brachycera, Cyclorrhapha, and Schizophora) and corroborate contentious findings, such as the anomalous Deuterophlebiidae as the sister group to all remaining Diptera. Our findings reveal that the closest relatives of the Drosophilidae are highly modified parasites (including the wingless Braulidae) of bees and other insects. Furthermore, we use micro-RNAs to resolve a node with implications for the evolution of embryonic development in Diptera. We demonstrate that flies experienced three episodes of rapid radiation-lower Diptera (220 Ma), lower Brachycera (180 Ma), and Schizophora (65 Ma)-and a number of life history transitions to hematophagy, phytophagy, and parasitism in the history of fly evolution over 260 million y.T he history of life is often portrayed as an ongoing series of evolutionary bursts, with each representing the origin and diversification of unique life forms with different and ecologically significant adaptations. Although the radiations of some groups, such as cichlid fishes of the lakes of East Africa or Darwin's finches, are well documented (1), the big radiations that account for most of the diversity of life on Earth have been more challenging to explore. To understand these radiations, we must resolve the relationships among major taxa, date the origin of these lineages (many of them ancient), and then explicitly consider whether the diversification events are really pulse-like adaptive radiations or, more simply, the result of nonadaptive, or even random, neutral processes.Although the paradigm of adaptive radiation has been applied to every level of biological classification, the large-scale macroevolutionary pattern expected from ancient repeated episodes of adaptive radiation is unclear. It has been predicted that at this scale, ecologically driven diversification may result in (i) significant variation in clade size, uncorrelated to the age of the clade (2), and (ii) shifts in average diversification rate coincident with major shifts in morphology, life history, or ecology (3). Another macroevolutionary prediction of repeated adaptive radiation is the widespre...

A cladistic analysis of the Empidoidea and basal lineages of the Cyclorrhapha, based on morphological characters, confirms the monophyly of both groups as well as that of the                    Eremoneura. The resulting final trees are used to revise the classification of the Empidoidea to include the following five families: Empididae, Hybotidae, Atelestidae (including Nemedininae n. subfam.), Brachystomatidae rev. stat. (comprising the subfamilies Brachystomatinae, Ceratomerinae and Trichopezinae), and Dolichopodidae s.lat. The family Microphoridae is not recognized, and the Microphorinae and Parathalassiinae are assigned to the Dolichopodidae s.lat. The Dolichopodidae s.str. includes 15 subfamilies that were previously recognized within the family. Within the Empidoidea we found support for Atelestidae as the sister group to the Hybotidae and for the monophyly of Parathalassiinae + Dolichopodidae s.str. The Empididae remains poorly defined and the genera Homalocnemis Philippi, Iteaphila Zetterstedt, Anthepiscopus Becker, and Oreogeton Schiner are classified as incertae sedis within the                   Empidoidea. In addition, the following higher taxa are proposed: Symballophthalmini n. tribe, Bicellariini n. tribe, Oedaleinae rev. stat., and Trichininae rev. stat., which are all assigned to the Hybotidae. The genus Sematopoda Collin is tentatively assigned to Trichopezinae, and Xanthodromia Saigusa is transferred from Hemerodromiinae to Brachystomatinae.        All morphological characters are extensively discussed and illustrated, including details of the antennae, mouthparts, internal thoracic structures, wings, and male and female terminalia. In addition, a key to families and unplaced genus groups of the Empidoidea is provided. Feeding habits are also discussed in terms of the empidoid ground plan condition.

Asymmetries are a pervading phenomenon in otherwise bilaterally symmetric organisms and recent studies have highlighted their potential impact on our understanding of fundamental evolutionary processes like the evolution of development and the selection for morphological novelties caused by behavioural changes. One character system that is particularly promising in this respect is animal genitalia because (1) asymmetries in genitalia have evolved many times convergently, and (2) the taxonomic literature provides a tremendous amount of comparative data on these organs. This review is an attempt to focus attention on this promising but neglected topic by summarizing what we know about insect genital asymmetries, and by contrasting this with the situation in spiders, a group in which genital asymmetries are rare. In spiders, only four independent origins of genital asymmetry are known, two in Theridiidae (Tidarren/Echinotheridion, Asygyna) and two in Pholcidae (Metagonia, Kaliana). In insects, on the other hand, genital asymmetry is a widespread and common phenomenon. In some insect orders or superorders, genital asymmetry is in the groundplan (e.g. Dictyoptera, Embiidina, Phasmatodea), in others it has evolved multiple times convergently (e.g. Coleoptera, Diptera, Heteroptera, Lepidoptera). Surprisingly, the huge but widely scattered information has not been reviewed for over 70 years. We combine data from studies on taxonomy, mating behaviour, genital mechanics, and phylogeny, to explain why genital asymmetry is so common in insects but so rare in spiders. We identify further fundamental differences between spider and insect genital asymmetries: (1) in most spiders, the direction of asymmetry is random, in most insects it is fixed; (2) in most spiders, asymmetry evolved first (or only) in the female while in insects genital asymmetry is overwhelmingly limited to the male. We thus propose that sexual selection has played a crucial role in the evolution of insect genital asymmetry, via a route that is accessible to insects but not to spiders. The centerpiece in this insect route to asymmetry is changes in mating position. Available evidence strongly suggests that the plesiomorphic neopteran mating position is a female-above position. Changes to male-dominated positions have occurred frequently, and some of the resulting positions require abdominal twisting, flexing, and asymmetric contact between male and female genitalia. Insects with their median unpaired sperm transfer organ may adopt a one-sided asymmetric position and still transfer the whole amount of sperm. Spiders with their paired sperm transfer organs can only mate in symmetrical or alternating two-sided positions without foregoing transfer of half of their sperm. We propose several hypotheses regarding the evolution of genital asymmetry. One explains morphological asymmetry as a mechanical compensation for evolutionary and behavioural changes of mating position. The morphological asymmetry per se is not advantageous, but rather the newly adopted mating po...

Homology of male genitalic structures in the lower Brachycera is examined and implications for the phylogenetic relationships of the included families are discussed in light of other characters. The following character states belong to the ground plan of the Brachycera: the aedeagus is enclosed in a parameral sheath; the sperm pump possesses paired articulated lateral sclerites, and a large ejaculatory apodeme with a terminal endoaedeagal process; the epandrium and hypandrium are separate; the hypandrium is separate from the gonocoxites; and the gonostyli articulate and move in the horizontal plane. The placement of Heterostomus in Xylophagomorpha is supported, based on modifications of the sperm pump. The presence ofaedeagal tines suggests that Bolbomyia, which is currently placed in the Rhagionidae, may be more closely related to Athericidae + Tabanidae. The expanded first segment of the female cercus supports the monophyly of the Tabanomorpha, including Vermileonidae. The transfer of the Pantophthalmidae to the Stratiomyomorpha is confirmed on the basis of modifications of the sperm pump. The Stratiomyomorpha is hypothesized to be the sister group of the Muscomorpha (sensu Woodley 1989) based on the apomorphic development of a composite structure termed the phallus. The monophyly of the Muscomorpha is supported by gonostyli that articulate and move obliquely or dorsoventrally. The presence of acanthophorites in females is considered apomorphic for the Heterodactyla (Bombyliidae + Asiloidea + Eremoneura). Bombyliidae (exclusive of Mythicomyiinae and Heterotropus) is defined on the basis of reduced gonocoxal apodemes. Gonostyli retracted to a subapical position and a hinged larval metacephalic rod are considered apomorphic for the Asiloidea (exclusive of Bombyliidae) + Eremoneura. Hilarimorpha and Apystomyia are removed from the Bombyliidae based on the subapical placement of the gonostyli, and together with Apsilocephala are placed as incertae sedis in Therevidae. Apiocera is considered the sister group to the remaining apiocerids + Mydidae on the basis of absence of gonostyli and lateral ejaculatory processes in the latter lineage.

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