Studies in Hawaiian Diptera III: New Distributional Records for Canacidae and a New Endemic Species of Procanace

Abstract The distributions of Hawaiian Canacidae, comprising nearly 800 individual collection events, are reviewed and a total of four new island records are reported. These include Canaceoides angulatus from Kahoolawae and Procanace bifurcata from Molokai and Maui, and Procanace constricta from Oahu. A new species from Kauai, Procanace hardyi O'Grady and Pak, is described. This species is closely related to P. constricta from Oahu, Maui, Molokai and Hawaii and shares a similar constriction of the abdomen between tergites four and five but differs in the configuration of the seventh abdominal tergite. Detailed distribution maps for all species are included.


Introduction
Canacidae, or the beach flies, surf flies and surge flies, is a relatively small family of acalyptrate Diptera primarily found throughout coastal regions of the world. A number of catalogs and revisions have been published in the past 20 years. Traditionally, this group contained only members of the family Canacidae, sensu stricto. The Mathis (1992) catalog of this family consisted of 113 species in 12 genera and recognized three subfamilies (Canacinae, Nocticanacinae, Zaleinae). Mathis and Munari (1996) transferred Zaleinae to Tethinidae when they published their tethinid catalog because this subfamily was considered intermediate between the two families. According to their definition, Tethinidae included 126 species in 14 genera arranged into five subfamilies (Apetaeninae, Horaismopterinae, Pelomyiinae, Tethininae, Zaleinae). McAlpine (2007) significantly altered the concept of this family when he included the family Tethinidae as part of a broader Canacidae sensu lato. Finally, Munari and Mathis (2010) updated the previous catalogs and now recognize six subfamilies comprising a total of 307 species in 27 genera within the Canacidae.
Five canacid genera are present in Hawaii (Nishida 2002 ), most of which are represented by only one or two species and were introduced by human activities in the past 100 years. Two genera within the subfamily Tethininae are present in Hawaii, Dasyrhicnoessa and Tethina. These were recently reviewed and updated by Munari and Evenhuis (2011) and the distributional records will not be repeated here. The genus Dasyrhicnoessa contains a total of 28 species, 22 of which are found in the Pacific and four of which are present in Hawaii (Evenhuis 2012, Hardy and Delfinado 1980, Munari and Mathis 2010, Munari and Evenhuis 2011. Dasyrhicnoessa insularis was first collected in Hawaii in 1923 and is widespread in Polynesia, Micronesia, Papua New Guinea, Central and South America and the Afrotropics (Evenhuis 2012, Hardy and Delfinado 1980). Hardy and Delfinado (1980) were unable to place the second species, D. vockerothi, in the literature and described it as a new species from Hawaii. Subsequent collections have found this species on islands throughout the Pacific and Indian Oceans, as well as in Japan and Australia (Evenhuis 2012). Finally, Munari and Evenhuis (2011) reported two additional species from Hawaii, D. clandestina and D. fulva. The genus Tethina is large, with 78 so far described species worldwide (Munari and Mathis 2010). Ten species are known from the Pacific, including three species from Hawaii. Hardy and Delfinado (1980) listed T. variseta from the Hawaiian Islands, a species that has since been synonymized with T. willistoni (Munari and Mathis 2010). Two other species, T. albula (Evenhuis 2012, Munari andMathis 2010) and T. pallipes (Munari and Evenhuis 2011) have also been reported in Hawaii.
A single genus of the subfamily Pelomyiinae, Pelomyia, is found in Hawaii. Pelomyia contains a total of 29 species, mostly found in the Nearctic and Neotropical regions. Hardy and Delfinado (1980) described P. steyskali from material collected in Hawaii and the west Coast of North America. This species has since been synonymized with P. occidentalis, a widespread taxon that is known from Nearctic, Neotropical and Palearctic regions (Evenhuis 2012, Delfinado 1980, Munari andMathis 2010).
The remaining two canacid genera present in Hawaii, Canaceoides Cresson and Procanace Hendel, are both in the subfamily Canacinae. These two genera can be found in a range of habitats, from the coastal aquatic environments to high elevation freshwater streams. They are most likely the result of at least two separate colonization events (Wirth 1969). The genus Canaceoides was last revised by Wirth (1969) and contains 9 species, all of which are either found on Pacific Islands or are distributed along the west coast of North and South America. Two species are recorded from Hawaii, C. angulatus and C. hawaiiensis ( Table 1). Wirth (1969) suggested that the widespread distribution of C. angulatus, which is found throughout the Hawaiian Archipelago and Peru, Mexico and the Galapagos Islands (Evenhuis 2012), is evidence for this taxon arriving in Hawaii prior to human contact. He proposed, however, that this was more recently than C. hawaiiensis, a species found exclusively in the younger Hawaiian Islands. The biogeographic history and evolutionary relationship of these two species is unclear. The male genitalia of C. angulatus is quite distinct for the genus and its sister relationships are not known. Likewise, Wirth (1969) states that C. hawaiiensis "has no exact counterpart on the American coasts." It is possible that these two taxa represent two distinct colonizations of Hawaii. Alternatively, these two species could represent a single colonization of Hawaii, with C. hawaiiensis being a recently divergent sibling species of C. angulatus. Phylogenetic analyses will need to be undertaken to differentiate between these two hypotheses. Aside from the early collections made by D.E. Hardy, W.W. Wirth and others, there are a number of surveys conducted by D. Polhemus and R. Englund for the Bernice P. Bishop Museum in the early 1990s (e.g., Polhemus 1992, Polhemus 1993   Habitus of the holotype female of P. hardyi in lateral view.  External male genitalia of P. hardyi. The narrowed, lightened tips of the surstyli suggest that this species is most closely related to P. constricta. Refer to figure 162e from Hardy and Delfinado (1980). Abdomen of P. hardyi female, showing constriction between tergites 4 and 5, the telescoping form of tergite 8 and the ovipositor and associated structures.

Diagnosis
This species is most closely related to Procanace constricta from Maui, Molokai and Hawaii. It is differentiated most readily by the shape of tergite seven. In P. constricta tergite seven is greatly expanded on the lateroventral margins and extends to the apices of the cerci (Fig. 6 ). The seventh tergite of P. hardyi (Fig. 5) is not expanded on the lateroventral margins and has a telescoping form typical of the other members of this genus. The ovipositor of P. hardyi is long and narrow, about two times longer than wide, with distinct setae at the apices. The width and length of the cerci in P. constricta is roughly equal and the setae at the apices of the cerci are short and inconspicuous.

Etymology
It is a pleasure to dedicate this species to the memory of Dr. D. Elmo Hardy.

Distribution
This species is endemic to Kauai (Fig. 7). Abdomen of P. constricta female, showing constriction between tergites 4 and 5, the lateral extension of tergite 8 beyond the apex of the ovipositor, and the ovipositor and associated structures. The specimen imaged is from collection 205268.
Hawaiian Islands.
Wing of Canaceoides hawaiiensis, showing a single break at the terminus of the subcostal vein. The specimen imaged was from collection 205542.   addressing the taxonomy of Tethininae and Pelomyiinae. Dr. Neal Evenhuis provided us with a number of unpublished Bishop Museum reports and a wealth of acerbic comments.