US Fish and Wildlife Service

Report on and Collected during the 2010 Field Season

by Steven R. Dawes Biological Technician

Introduction

Benton Lake National Wildlife Refuge has little record of potential invertebrate populations with regards to dragonflies and damselflies (bnl_bioinventory_aug08.xls). We collected adult dragons/damsels from 24 June through 2 September 2010 for the purpose of attaining a reference collection for the Refuge and a display collection for the Visitors Centre. No permits were required to collect specimens.

Study Area

Benton Lake NWR is a 12,383 acre refuge on the western edge of the northern Great Plains, 12 miles north of Great Falls, MT. Benton Lake itself is a 5,000 acre closed marsh basin, terminus of a 145 square mile watershed. Terrain is gently rolling with short-grass native prairie predominating. The lake basin has been diked into 8 marsh units to provide better water control for submergent and emergent vegetation and to limit botulism outbreaks. The refuge supports a diversity of wetland habitats.

Methods

The flight season for damselflies ranges from May-November, for dragonflies, May-October. A set quota of 6 specimens of each species, 3 male and 3 female, was established. Procedures for collecting, identifying, preserving, and storage followed those outlined in, Dragonflies and Damselflies of the West by Dennis Paulson, pages 32-34 inclusive. were initially caught using a 15" diameter heavy duty sweep net. It quickly became apparent this style net was too cumbersome so the switch was made to an aerial hoop net of the same size. Insects were caught by sweeping them from perches, on the fly (very difficult), or by dropping the net on top of the insect. With the latter method, once the net was grounded the apex of the net was lifted to its full height. This causes the insect to fly up into the net making locating it within and extraction from the net much easier. After capture, specimens were placed singly, with wings folded back, in #3 coin envelopes. Specimens were identified with the collector’s initials and sequentially numbered with the last two digits of the year followed by the specimen number, for example, srd 10-23, (2010, the 23 insect caught). If insects were caught in tandem or in copula this information was recorded on both envelopes. Additionally, the type of insect, dragon or damsel, and the sex were also recorded on the envelope. As experience was gained a limited number of specimens could be identified to species in the field and this information was also written on the envelope. The following information was recorded in a field log: date, type of insect or species, sex, serial number, GPS point, and the predominate vegetation the specimen was captured in. All information on the coin envelopes and in the field log was recorded using indelible ink. A GPS point was taken for each insect caught in order to plot species distribution. A 4-letter alpha code, based on a specie’s colloquial name, was devised to simplify record keeping. The complete 4-letter alpha code list of all odonates is included in appendix 1. Specimens were left in the envelopes for a few hours to void their stomach contents, then killed by immersion in an acetone bath. After death, the specimen was inspected to ensure the abdomen was straight, wings either folded back or spread, and legs folded under the body. The specimen was returned to its envelope and re-immersed in acetone for 12-24 hours. Acetone extracts fat and water ensuring better preservation than air-drying. Specimens were then removed from the bath and air-dried for several days allowing the acetone to evaporate. A respirator with appropriate organic solvent cartridges and latex disposable gloves were worn when working with the acetone. Specimens were then inserted into a polypropylene sleeve with the following information attached to a 3x5 index card by use of an adhesive label: species name, both colloquial and scientific, 4-letter alpha code, sex, state, county, and locality where caught, lat/long, immediate vegetation, date, and field number with collector’s initials. The envelopes were sealed using a poly bag impulse sealer. Separated into suborders and families the sealed envelopes were stored in a 4x6 index card file.

Results

Seven species in 2 families were found (Table 1). : Variable Darner ( interrupta). : Eight-spotted Skimmer ( forensis), Twelve-spotted Skimmer (L. pulchella), Variegated Meadowhawk ( corruptum), Striped Meadowhawk (S. pallipes), Cherry-faced Meadowhawk (S. internum), and Band-winged Meadowhawk (S. semicinctum). Four species in 2 families were found (Table 1). : Spotted Spreadwing ( congener), Lyre-tipped Spreadwing (L. unguiculatus), and Emerald Spreadwing (L. dryas). : ( boreale). Information on each insect caught in both suborders is numerically catalogued in appendix 2. The set quota of 6 specimens of each species, 3 male and 3 female, was exceeded by a factor of 2 in some cases due to inexperience on part of the collector.

Discussion

According to the checklist of Montana Dragonflies & Damselflies, jointly printed by Montana Fish, Wildlife, and Parks and the Montana Natural Heritage Program, there are 20 dragonfly and 17 damselfly species in what the checklist refers to as north central Montana. Benton Lake NWR falls within this area. However, only 7 dragonfly and 4 damselfly species were collected. It is not known if more species are present as this is the first comprehensive attempt to determine populations at Benton Lake. There may be as many as 17 more species of both suborders present based on region and habitat (Nathan Kohler, pers. comm.). Dragonflies and Damselflies are habitat specialists and can be found in a wide variety of places. As a result dragons and damsels were captured in several locations throughout the Benton Lake NWR (Table 2). Although odonates are aquatic , a number species of both suborders were found at locations not immediate to water. The section of the refuge east of the Bootlegger Trail is an example. This is not unusual as most species leave the waterside when immature and will range a fair distance, even miles, from it (Paulson, 2009). Adult dragons and damsels do not emerge from larval forms with full adult colours. This can lead to confusion and misidentification, especially in the field where a fuller range of diagnostic tools will not be available. Colours will change overtime deepening and darkening with age, to a point, then fading as the aging process continues to death (Paulson, 2009). The ease or harshness of life can also affect the appearance of adults. As a result immature adult specimens may look very different from older adults. Additionally, we noticed that immatures of different species can look similar as well. This was most problematic with meadowhawks. Identification is best made by the viewing of species specific sex organs (Paulson, 2009). However, pictures or drawings of these structures are not always available. Collection will continue in 2011 and subsequent years so a complete profile as possible of odonata species at Benton Lake can be known. The problem of over collection will be addressed by the formation of a field guide tailored to Benton Lake NWR. It will include species known to the refuge and those which should occur based on the region and various habitats found on the refuge. Colour photographs especially of immature animals, if available, detailed descriptions, and pictures or drawings of sex organs will be included. Additionally, a current list broken down by species, sex, and numbers caught will also be carried in the field.

Table 1. Dragonfly and Damselfly families and species caught at Benton Lake NWR, 2010.

Dragonflies

Aeshnidae

Variable Darner (Aeshna interrupta) (VADR)

Libellulidae

Eight-spotted (Libellula Skimmer (8SS) forensis)

Twelve-spotted (Libellula Skimmer (12SS) pulchella)

Variegated (Sympetrum Meadowhawk (VAMH) corruptum)

Striped Meadowhawk (Sympetrum pallipes) (STMH)

Cherry-faced (Sympetrum internum) Meadowhawk (CFMH)

Band-winged (Sympetrum Meadowhawk (BWMH) semicinctum)

Damselflies

Lestidae

Spotted Spreadwing (Lestes congener) (SPSW)

Lyre-tipped (Lestes Spreadwing (LTSW) unguiculatus)

Emerald Spreadwing (Lestes dryas) (EMSW)

Coenagrionidae

Boreal Bluet (BOBL) (Enallagma boreale) Table 2. Locations where Dragonflies and Damselflies were captured at Benton Lake NWR, 2010.

Unit 1

Unit 2

Unit 4A

Unit 4C

5/6 Dike

West Road

Shelter Belts 1A, 14,

South Patrol Road

East of the Bootlegger Trail

Appendix 1. 4-letter alpha codes for Montana odonates.

Odonata of Montana

12SS Twelve-spotted Skimmer OCEM Ocellated Emerald 4SS Four-spotted Skimmer PADN Paiute Dancer 8SS Eight-spotted Skimmer PAFT Pacific Forktail ALBL Alkali Bluet PAST Pale Snaketail AMEM American Emerald PHCT Pronghorn Clubtail AMRS American Jewelwing PLCT Plains Clubtail ARBL PLEM Plains Emerald AUMH Autumn Meadowhawk PRBL Prairie Bluet BEDR Blue-eyed Darner PSPT Pacific Spiketail BEWF Belted Whiteface PTDR Paddle-tailed Darner BLMH Black Meadowhawk RBBL Rainbow Bluet BOBL Boreal Bluet RIBL River Bluet BOWF Boreal Whiteface RIEM Ringed Emerald BSCT Brimstone Clubtail RIJW River Jewelwing BTDR Black-tipped Darner RVMH Red-veined Meadowhawk BTEM Brush-tipped Emerald SABL Subarctic Bluet BWMH Band-winged Meadowhawk SADR Subarctic Darner CADR Darner SEDR Sedge Darner CFCO Chalk-fronted Corporal SESP Sedge Sprite CFMH Cherry-faced Meadowhawk SFSW Sweetflag Spreadwing CGDR Common Green Darner SHDR Shadow Darner CLDR Darner SIST Sinous Snaketail COWT Common Whitetail SPBT Spiny Baskettail CRWF Crimson-ringed Whiteface SPSW Spotted Spreadwing DTWF Dot-tailed Whiteface SRCR Swift River Criuser EAFT Eastern Forktail STMH Striped Meadowhawk EART Eastern Ringtail SWMH Saffron-winged Meadowhawk EBSW Ebony Jewelwing TABL Taiga Bluet EMDN Emma’s Dancer TUBL EMSW Emerald Spreadwing VADN Variable Dancer FABL VADR Variable Darner FLSK Flame Skimmer VAMH Variegated Meadowhawk HABL Hagen’s Bluet VIDN Vivid Dancer HOCT Horned Clubtail WAGL Wandering Glider HUEM Hudsonian Emerald WEFT Western Forktail HUWF Hudsonian Whiteface WEMH LADR Lake Darner WEPH Western Pondhawk LTDR Lance-tipped Darner WFMH White-faced Meadowhawk LTSW Lyre-tipped Spreadwing WHEM Whitehouse’s Emerald MABL WRDL Western Red Damsel MOEM Mountain Emerald ZZDR Zigzag Darner NOBL Northern Bluet NOSW Northern Spreadwing