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 and Mathis 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, Hardy and Delfinado 1980, Munari and Mathis 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).

The genus Procanace contains 30 species, found in the Palearctic, Nearctic, Australasian/Oceanian and Afrotropical regions. The Oceanian taxa include a small radiation of eight described species present in Hawaii (Table 1). Of these taxa, seven are endemic and one, P. williamsi, is known from Oahu and Japan (Evenhuis 2012). It is possible that P. williamsi was introduced to Hawaii in the 1940s and has since failed to establish in Hawaii, a common phenomenon among adventive species (Kolar and Lodge 2001). Two individuals are reported by Wirth, one taken at a light on Oahu and another taken in a plane. Additional collections will be required in order to determine the status of P. williamsi.

The endemic Procanace species are found on all the high Hawaiian Islands. There is one widespread species, P. bifurcata, found across the islands. The remainder of the species are found either on the "old" islands of Oahu and Kauai in the northwest and the "young" islands of the Maui Nui complex (Maui, Molokai, Lanai, Kahoolawe) and Hawaii in the southeast (Table 1​). For example, P. hardyi, P. nigroviridis, P. quadrisetosa, and P. wirthi are present on the older islands in the archipelago. These are mostly single island endemics, although P. wirthi is found on both Oahu and Kauai. In contrast, P. acuminata, P. confusa, and P. constricta are found on Maui Nui and Hawaii. These species are not single island endemics and can be found on multiple islands of the Maui Nui group and/or on Hawaii. This difference in distribution pattern may be because of the recent connections between Maui, Molokai, Lanai and Kahoolawae (Price and Elliott-Fisk 2004​). Alternately, it might be because the Big Island of Hawaii is less than 500,000 years old and speciation has yet to take place between founder populations on Maui Nui and descendant populations on Hawaii.

The endemic Hawaiian Procanace are notable within the genus and the family for their adaptation to freshwater, rather than saltwater, habitats. Hardy and Delfinado (1980) listed seven described endemics (P. acuminata, P.bifurcata, P. confusa, P. constricta, P. nigroviridis, P. quadrisetosa, P. wirthi) and one additional species from the island of Hawaii that they did not describe. Here we describe a new species from Kauai, Procanace hardyi O'Grady and Pak, bringing the total Hawaiian Procanace to nine (eight endemic and one adventive) described and one underscribed species.

Literature Review

Collection Methods