Mongolia Chironomid Database

Chironomid samples were collected in several ways, from various habitats at each site. Sites and associated water-quality samples correspond to those identified in the Environmental Database.

For further information, please contact Len Ferrington and visit his Mongolia chironomid web page.

Methods for Collecting and Processing Chironomidae
Leonard C. Ferrington Jr. & R.W. Bouchard Jr.

Collecting Methods

Chironomidae were assessed using four methods appropriate for collecting adults, pupal exuviae and larvae. Flying adults were collected using sweep netting of aerial swarms and by disturbing vegetation. Adults observed resting on substrates, tents or vehicles were aspirated directly into sample jars. Pupal exuviae left behind by recently emerged adults were collected from flotsam in littoral zones, among floating vegetation, and from windrows of detritus on leeward shores using the method described by Ferrington et al. (1991). Larvae were removed from dip-net samples used to assess Ostracoda and from dredge samples collected for analysis of diatoms and charcoals. The different sampling approaches compliment each other to provide more comprehensive assessments of chironomid species richness, but only sweeping, aspirating and collecting pupal exuviae were consistently employed across all lakes. Collections of pupal exuviae most consistently provided higher estimates of species richness on a lake-by-lake basis, and contributed substantively to the total species estimate for all lakes. Consequently, the method is described in more detail in the next paragraph, and the methods paper by Ferrington et al. (1991) is available on-line.

Field collection of surface-floating pupal exuviae (SFPE) was accomplished by dipping a white plastic pan (17 cm x 24 cm inside diameters) into the water in areas where pupal exuviae were accumulated by wind and wave action. Water, detritus and floating pupal exuviae flowed in as one edge of the pan was dipped beneath the surface of the water. After the pan filled with water, the contents were then poured into a U.S. Stan-dard Testing Sieve with an aperture of 125 microns. Detritus and exuviae were retained by the sieve. The entire procedure of dipping and sieving was repeated until a large amount of detritus and exuviae was accumulated in the sieve. Windrowed material on shorelines was re-suspended before sampling by pouring water onto the detritus and washing it back into the littoral zone to allow mineral sediments to sink before dipping and sieving. The contents of the sieve were then transferred to a sample jar, labeled and field preservative of 95% ethanol was added. Exuviae were sorted from detritus in the laboratory under 12X magnification in order to insure that specimens of small species were found and removed.

Sample Processing

All specimens in samples of SFPE with less than 300 exuviae were examined, sorted to genus, and exemplars of each species slide mounted in Euparol® and identified. Larger samples were randomly subsampled to 300, then slide mounted in batches for identification using a compound microscope at higher magnification.

Adults were cleared and dissected before permanent slide mounting similar to the procedure described in Sæther (1969). Identification to genus was accomplished using Wiederholm (1989, for adults) or Coffman & Ferrington (1996, for pupal exuviae and larvae), or was based on associated or partially associated specimens. Identification to species, when possible, was accomplished with reference to the most recent taxonomic revision for the genus, or was based on partially associated specimens. Several taxa did not match the formal descriptions in the most recent generic revision and are considered to represent undescribed species. Consequently, no species names are formally assigned for these taxa at this time, and they are referred to as sp. 1, sp 2, etc., or they are listed as sp. near a described species, or are only identified to a species group. Voucher specimens of all taxa are deposited in the Insect Collection of the Department of Entomology at the University of Minnesota.

Data Availability

The following data file is available to download in MS Excel (*.xls) format:
ChiroSiteID Sample number, location, sample type, and habitat.

In addition, the following identification key is available as a PDF: Identification Guide and Key to Chironomid Pupal Exuviae in Mongolian Lakes, by R. William Bouchard, Jr., and L.C. Ferrington, Jr.