11 Notul. odonatol., Vol. I, No. 1,pp. 1-16, June 1, 1978 Notes on the dragonfly fauna of very small pools near Münster, Westfalia, German Federal Republic R. Rudolph Lehrgebiet Biologie,Pädagogische Hochschule, Fliednerstr. 21, D-44 Münster, German Federal Republic Abstract — The odonate fauna of small ous differences between the findings of meadow pools was recorded for several these authors and mine, as far as faunistics years. Even the permanent pools cenoses are are concerned. relatively poor; Lestidae are completely lacking. Pyrrhosoma nymphula and Ery- Vegetation thromma najas dominate in clean waters, Several types of meadow pools can be whereas Ischnura elegans withstands a cer- distinguished: tain of Adult degree pollution. Anisoptera (1) Shallow water of more or less astatic are absent, save for Anax imperator, which nature. Sparse vegetation of Juncus, established territories even at the smallest and like Poa and Lemna, algae, grasses bodies of water. Alopecurus spp. (2) Deep water of permanent nature. Sub- Introduction made Ranun- merged vegetation up by This paper attempts to give a concise survey, culus aquaticus, R. trichophyllus, Pota- with ecological notes, of the dragonfly mogeton natans, Polygonum amphi- small cenoses of very pools, quite a lot of bium, Myriophyllum spicatum, Juncus which be found in the meadows and Lemna and filiform can effusus, spp. algae. Munster. used pasture land around They are (3) Unfenced pools. Vegetation partly as watering places for cattle. Some of these destroyed by trampling cattle. Ex- crements of cattle influence pools are bomb holes of characteristic cir- badly outline. water cular I have been surveying a num- quality. ber of these pools for several years with res- (4) Fenced-in pools with additional vegeta- pect to their dragonfly fauna and vegeta- tion at the water edge, represented tion. by Carex spp., Typha spp., Sparganium Iris In the literature there are only very few erectum, pseudacorus, Alisma plan- ecological notes on the dragonfly fauna of tago-aquatica and meadow grasses. abundance small stagnant water bodies in Central Species composition and in Europe, either natural or artificial. The most the plant communities of course differ. the of small Some with profound approach to ecology pools are completely overgrown meadow pools in Northern Germany similar one plant species, e.g. Ranunculus aquatilis, those considered in is the Lemna. to my own paper, Alopecurus aequalis, or just Phrag- of mites extensive work KREUZER (1940), deal- is not found in any of these pools. also with Odonata. MUNCHBERG No ing bushes or trees are growing at the water recorded 3 in (1956) only species breeding edge ofany of these pools. bomb holes. DUMONT (1971) gave a de- tailed account of the dragonfly fauna of Chemism bomb holes other artificial some among Small pools are distinguished by extreme water bodies in Belgium. Miinchberg and circadian and seasonal changes in the con- Dumont dealt with the cenoses of both centration of certain ions, partly due to FISCHER of larvae and adults, while (1961) photosynthesis, partly as a mere effect in water concentrated on dragonfly larvae small evaporation. However, in some pools in pools Poland. There are some conspicu- considered here, concentration changes are 12 Notul. odonatol., Vol. I, No. 1, pp. 1-16, June 1, 1978 due increased influx Aeshna more markedly to an cyanea (Mull.), Anax imperator of ions after bringing out artificial fertilizer, Leach, Libellula quadrimaculata L., Sym- dung or liquid manure on the surrounding petrum flaveolum (L.), S. vulgatum (L.), S. of land. Coincidence changes in ion concen- sanguineum (Mull.). tration and electric conductivity with agri- It is possible that some other species but cultural procedures could be ascertained regularly reproduce in these pools, never at even large ponds of various size (RU- reach appreciablenumbers of larvae, and are DOLPH, 1978). Out of a greater body of thus easily overlooked. This holds for Ani- chemical data collected over a year’s period soptera e.g. Aeshna grandis (L.) and Cordu- winter of bomb hole (except months) one lia aenea (L.), which in the adult stage do located in meadows, some are listed in Table not establish territories at the pools because I. of the small size and unsuitable vegetation, so that there is nearly no chance to meet Table I. Some data chemical of pool 1. (All them as adults at the pools. for figures ions in mg/1; oxygen concentra- Above all, species number and popula- tion was measured only once in March, tion density at the pools depended on the 1977) more or less astatic nature of the water body. FISCHER (1961) has stressed the fact 1976 1977 that in those astatic ponds she investigated Month 7 8 3 5 6 8 10 in the Lestidae outnumbered the PH 7.5 8.1 7.7 7.6 7.4 7.6 8.1 Poland, nitrite 0.035 0.05 0.022 0.005 0.005 0.04 0.025 Coenagrionidae. Of course the univoltine nitrate 1.77 0.39 0.88 0.16 0.32 0.16 0.29 0.06 ammonia 0.38 0.26 2.10 0.22 0.22 0.18 Lestidae are largely adapted to survive in 0.04 0.04 0.04 phosphate 0.22 - 0.09 0.03 astatic but of sulfate 36 83 79 255 36 waters, as a matter fact, no oxygen 9.36 Lestidae found of the meadow were at any pools within 5 years. This is in contrast to In meadow pools the pH value in most the findings of Fischer, KREUZER (1940), is and cases definitely alkaline, even in times my own observations of Lestidae at of reduced photosynthetic activity. Electric astatic waters of slightly different chemical conductivity is permanently high, signalling character and differing location in the Mun- ster a great amount of ions in solution. Dragon- area. So far no reason can be given for the of from fly larvae are not affected by high ion con- absence Lestidae small meadow Libellula to centrations or rapid concentration changes, pools. depressa L., too, is said but actually nothing is known about the withstand drying up of its habitats, but no larvae have been found. In effect particularly on dragonfly larvae of our region this species is one H2S, NO2, NH3 and NH4, which are rare, and only single male either toxic involved in was ever met at a particular pool. directly or oxygen consuming nitrification processes. These Though occasionally larvae of semivol- ions are surely limiting factors, and their tine species like Pyrrhosoma nymphula, Libellula negative effect is demonstrated at those Aeshna cyanea and quadrimaculata found in unfenced pools, which are polluted with were pools drying up regularly the univoltine cattle excrements and lacking almost any only Sympetrum species are water arthropods. likely to survive in these habitats. Larvae of Sympetrum species and of Libellula quadri- The dragonfly fauna maculata were met with even in pools Larvae of the following eurytopic species devoid of all macrophytes except flooded were found inhabiting small meadow pools: grass. Pyrrhosoma nymphula (Sulz.), Ischnura Pyrrhosoma nymphula, although not elegans (Vander L.), Enallagmacyathigerum confined to narrow ecological limits, does (Charp.), Coenagrion puella (L.), C. pulchel- not by far inhabit all permanent pools with lum (Vander L.), Erythromma najas (Hans.), sufficient vegetation. So far the distribution Notul. odonatol., Vol. I, No. 1, pp. 1-16, June 1, 1978 13 pattern of this species cannot be explained. bers. Of S. flaveolum, S. vulgatum and L. DUMONT (1971) suggested that P. nym- quadrimaculata only a few larvae were phula is expelled from potentialhabitats by caught. competition of Coenagrion pulchellum and The cenosis of the adults is completely but both these Enallagma cyathigerum, different.I elegans dominates here as well, species are only very seldom met with at the followed by C. puella and E. najas, but meadow pools in Westfalia. Here dense Anisoptera are encountered only very sel- with populationsI.of P. nymphula coexist dom, except for A. imperator and a few elegans, C. puella and Erythromma najas. Sympetrum individuals. DUMONT (1971) The latter species colonizes nearly all pools states that A. imperator prefers large water with adequate habitat structure, i.e. floating surfaces and, therefore, does not inhabit the macrophytes. bomb holes investigated by the author, As could be the more diversi- while A. finds sufficient ’’elbow expected, cyanea fied dragonfly cenoses of both larvae and room” even at the smaller bomb holes. On adults are found at less polluted permanent the contrary, in our region, A. imperator pools with great productivity, i.e. dense is the only anisopterous species permanent- in small vegetation and rich arthropod fauna as a ly present the adult stage at very food supply. water bodies like the open meadow pools Two pools with their characteristic and bomb holes, provided that they offer cenosesshall be described in detail. erect growing plants to rest upon, like Typha and Iris. Obviously a pool of about Pool 1 only 5 m radius is of suffic it size to be m a as one Bomb hole of about 5 radius and depth occupied territory by ... imperator At of about 2 m. Protected from cattle. Con- male. one particular pool a male Anax stant water level. Dense vegetation of Jun- was observed on 9 successive days patrolling and the is not cus effusus, Carex pseudocyperus throughout day, but it sure various meadow about half of whether it was the same grasses covers specimen. In A. the water edge, with a few additional our region, cyanea prefers ponds Typha latifolia, Iris pseudacorus, Sparga- surrounded with bushes or trees. nium erectum and Alisma plantago-aquatica. The cenosis of the adult dragonflies is water the - About a third of the surface is cover- Erythromma najas Anax imperator ed with Potamogeton natans and Ranuncu- cenosis of JACOB (1969), which is rather lus trichophyllus.