Aquatic Insects of the West River and Salt Marshes ... - Yale University

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PUPEDIS 165bridge. Possibly, the aquatic insect community was being adverselyaffected by increased salinity levels produced as a consequence of dailytidal fluctuations of the river at this point. In addition to salinityeffects, the sandy bottom of the river bed and the large packs ofdecaying organic matter undoubtedly contributed to a decreaseddiversity of aquatic insects in the river and reflecting pool. However,shoreline populations of insects appeared rich in species and easilyinventoried. For these reasons, emphasis was placed on an inventoryof the semiaquatic shoreline communities, with less emphasis placedon the completely aquatic communities.Insect taxa to be included in the survey were based on the insectsthat were accessible, the time available for collection and curation,and the experts available for identifying specimens. Collecting focusedon the Coleoptera and Hemiptera. Insects from other groups werecollected when encountered, but they were not purposely targeted.The final species list undoubtedly lacks key species that may appearat different seasons or in zones not sampled adequately. A vouchercollection of insect specimens from the four sites, field notes, andcollecting maps have been deposited in the Entomology Division atthe Yale Peabody Museum of Natural History.RESULTSWEST RIVER MEMORIAL PARKApproximately 87 species representing 41 insect families fromeight orders were collected in West River Memorial Park (Appendix 1).There were few aquatic insects in the river. At the Chapel Streetbridge, species of mayfly nymphs (Ephemeroptera: Baetidae), adultand larval riffle beetles (Coleoptera: Elmidae), caddisfly larvae(Trichoptera: Hydropsychidae), larval black flies (Diptera:Simuliidae), midge larvae (Diptera: Chironomidae), and an adultsialid (Megaloptera: Sialidae) were found. Each of these groups wasrepresented by only one or two individuals.A numerically larger and more diverse aquatic community wascentered in a small side channel of the river that was somewhatisolated from the main river channel and tidal influences (Site A1,Fig. 1). Here, larval and adult specimens of dragonflies and damselflieswere collected along with various heteropterans, such as thepygmy backswimmers (Pleidae), shore bugs (Saldidae), waterboatmen (Corixidae), and creeping water bugs (Naucoridae).Beetles (Coleoptera) were represented by species from several aquaticfamilies: water scavenger beetles (Hydrophilidae), predaceous divingbeetles (Dytiscidae), whirligig beetles (Gyrinidae), and crawlingwater beetles (Haliplidae). The site exhibited insects that weretypical of a freshwater environment.YALE F&ES BULLETIN
166 INTERDISCIPLINARY RESTORATIONAquatic sites lower on the river within West River MemorialPark yielded only chironomid larvae (Diptera: Chironomidae) anda few water scavenger beetles (Coleoptera: Hydrophilidae). Otherresearchers involved in the West River biological survey also foundonly chironomid larvae in the lower West River (C. Cuomo, GeologyDepartment; J. Moore, Biology Department, Yale University,personal communications). The restriction of freshwater organismsto upper parts of the river was consistent with concurrent watersalinity data recorded by Cuomo and Zinn (this volume). Rainfalldata indicate an area-wide drought that began in 1993. The resultinglower water levels, coupled with the effects of an open tide gateduring 1995, undoubtedly contributed to elevated salinity levels.This effectively shifted the communities of freshwater insects fartherupstream, beyond the reach of tidal influence. Possibly, the currentaquatic community predicts the future insect community that willbe found when salinity levels rise to those sustaining a salt marsh.The shoreline communities on the mud and clay banks along theriver and reflecting pool were host to a diverse group of beetles andother insects. Thirty-two species from nine beetle families were discoveredat the waters’ edge. Of these, the species of the coleopterangenus Bembidion are well-known inhabitants of salt marshes(Olmstead and Fell 1974). On the eastern side of the central island, alarge colony of tiger beetle larvae Cicindela duodecimguttata Dejean(Cicindelidae) were discovered inhabiting clay banks adjacent to thereflecting pool. No tiger beetles were seen on the other sand bars inthe river during the collecting period.Taxa found at West River Memorial Park had little in commonwith the salt marsh communities. Nonetheless, several salt-associatedinsects were found in the park. Two carabid beetle species,Bembidion contractum Say and B. versicolor LeConte, and one cleridbeetle (Enoclerus rosmarus Say), collected in the park were alsofound in one or more salt marshes. Among the Diptera collected atthe West River, one Notiphila species (Ephydridae) was found alsoat the Hoadley and Pine Creek salt marshes. No new species or thoseconsidered by federal or state agencies to be endangered, threatened,or of special concern were encountered at the West River.Bembidion sp. (redrawn fromGreene 1968)NEW RECORDSDuring our collecting, a new state record was established for theseed bug Chilacis typhae (Perris) (Heteroptera: Lygaeidae). Thisexotic from Europe is restricted to the heads of cattails (Typha spp.).The first record of this species in North America was from Pennsylvaniain 1986 (Wheeler & Fetter 1987). In the West River, it wasBULLETIN 100
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