Ecological notes on Sympetrum madidum (Hagen) in British Colum- bia, Canada (Anisoptera: Libellulidae) R.A. Cannings Department of Entomology, British Columbia Provincial Museum,601 Belleville Str., Victoria, British Columbia, V8V 1X4, Canada Abstract — Some of the of S. 250 m 30 and dries aspects biology by m usually up by August; madidum in British Columbia are discussed it is refilled by winter rains. On June 16, 1979, and the habitat of its recently discovered larva the greatest depth was 75 cm although over 80 is described. The is cent of its it sp. apparently adapted to per area was less than 40 cm deep. that in midsummer. On this date the surface ponds may dry up conductivity was 160 micromhos/cm (at 25°C) and the pH was 7.0. Introduction The pond is in a trough in sandy soil forested Although Sympetrum madidum is a wide- with Douglas-fir( Pseudotsuga menziesii( Mir- spread western North American species, little bel) Franco), lodgepole pine (Pinus contorta is known of its biology. The larva has only Dougl.) Garry oak ( QuercusgarryanaDougl), been its and arbutus recently discovered; information on (Arbutus menziesii Pursh). Wil- habitat is provided here for the first time. low ( Salix sp.) borders some ofthe high-water line. in The pond is completely covered emer- Observations the gent vegetation; predominant plants are S. madidum larvae discovered Eleocharis & were at Spencer palustris (L.) R. S., Sium suave School Pond, Langford, British Columbia, 10 Walt., Polygonum amphibium L., Ranun- km west of Victoria, B.C. The pond is shallow. culus aqualilis L„ Nuphar polysepalum 98 Notul. odonatol., Vol. I, No. 6, pp. 97-112, December I, 1980 Engelm. and Carex rostrata Stokes. The latter between 1000 and 1200 micromhos/cm two in discrete while species grow patches (25°C). At a shallow temporary pond near the others rather distributed are evenly over Riske Creek, B.C., on June 29, 1978, a teneral the the The surface of pond. bottom is firm. female was found near what is now known to On June 16 at 11.30 h the surface water be an S. madidum larval exuvia. The and the temperature was 16°C air temperature dominant vegetation here was Eleocharis I4°C. was Final instar larvae were estimated surface palustris ; conductivity was approx- reach densities of about 20 2 Larvae of to per m . imately 600 micromhos /cm. On June 25, 1977, Lestes Sel. and disjunctus Limnephilus sp. at Witty's Lagoon, Victoria, B.C., females numbers. the (Trichoptera) were present in large were ovipositing in dried up basin of a No adult Sympetrum were seen. lagoon behind the beach. This pond is filled Larvae collected and kept in the laboratory with brackish water from fall through spring at a water temperature of 22°C (air tempera- by rainfall and water from the overflow of the between 06.30 h and ture 23.5°C) emerged nearby tidal estuary. E. palustris grew com- 13.30 h. monly in the pond basin. The eggs were around the bases Sympetrum madidum adults were first dropped on the mud of the observed emerging at SpencerSchool Pond in plants. Surface conductivity ofthis pond when small numbers June and few on 18-21. 1979, a it contained water on April 21, 1979 was 1045 adults about oneweek old also were captured. micromhos/cm. At both this location and the A single exuvia found on June 3 indicates the Clinton pond, oviposition was accomplished the occurred the the tandem the initial emergence of species in either while pair was in or while first week of Lestes the in the June. dryas Kirby was male hovered a guarding position near other only odonate emerging at this time. The female. major emergence of S. madidum, however, In summary. S. madidum is known to June Adults in took place on 23. began trans- oviposit and develop waters with surface about 10.00 160 1045 forming h, mostly at 5-10 cm conductivities ranging from to above the water on the stems of Nuphar, Sium micromhos/cm (at 25°C); both athalassic and Carex. Densities reached 10 per m2 . The saline ponds and coastal brackish waters are water temperature was 19°C and the air involved. In all four localities recorded, h temperature 20°C. After 11.30 many teneral Eleocharis palustris was one of the predomi- adults were flying, and at about 12.30 h a few nant plants. fully mature adult males appeared at the pond S. madidum, Lestes disjunctus and L. dryas and observed. Other the Odonata known one pair in copula was were only to develop in Odonata flying at the same time included Spencer School Pond in 1979. Allwere able to Lestes dryas mating and ovipositing, L. dis- emerge before the pond completely dried in S. junctus emerging in large numbers, and a few the first week of August. Individuals of I. rather Al- Ischnura cervula Sel., perparva Sel., Enal- madidum emerged synchronously. lagma cyathigerum (Charp.) and Libellula though a very few adults appeared at this pond quadrimaculata L. Cedar Waxwings ( Bomby- in the first three weeks of June, 1979, it is the cilia cedrorum Vieillot) nesting nearby were estimated that at least half population the feeding their young on the teneral S. madidum transformed on June 23, first day of and the whole L. disjunctus. concerted emergence. Evidently and recorded Copulation oviposition are population emerged by June 30. in British Columbia from June 23 (1979, Langford)to August 6 (1976, Clinton). At the Discussion females madidum is latter locality oviposited among In British Columbia S. apparently emergent Eleocharis palustris growing in the adapted to temporary ponds; it has been soft bottom, dipping their abdomens into 4-5 observed ovipositing in dry pond basins and in cm deep water. The pond margin was heavily shallow water that subsequently disappeared. trampled and polluted by cattle. The surface Since only very early instar larvae were found conductivity of this pond was estimated at at Spencer School Pond or Witty’s Lagoon in No. Notul. odonatol,, Vol. I, 6, pp. 97-112, December 1, 1980 99 April, 1979, it is probable that the species Acknowledgements — 1 thank Dr. G.G.E. overwinters in the egg and hatches in the SCUDDER for reading the manuscript. Dr. and spring, much as do S. obtrusum (Hag.) S. G.B. WIGGINS identified the Trichoptera rubicundulum (Say) in temporary waters larva, and Mr. E. MANSFIELD helped with Larval of the field (G.B. Wiggins, pers. comm.). growth some collecting. must thereafter be rapid. These same - collections of larvae in April yielded very Reference SAWCHYN, W.W. & N.S. small, uniformly sized larvae of Lestes CHURCH, 1973. Can. J. Zool.5\: 1257-1265. disjunctus and L. dryas which are known to the and hatch the diapause in egg in winter in Received November 5, 1979. spring (SAWCHYN & CHURCH, 1973)..