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 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 . 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 . 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 . 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.), 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 . 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 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. Dense submerged vegeta- characteristic for small meadow pools in our

tion ofMyriophyllum spicatum near to the region.

water edge. Chemical data of this pool are No changes in species composition of

given in Table I. Oxygen level is rather high. this cenosis were observed throughout the

Other invertebrate fauna is rich. A few whole period of investigations.

fishes (Scardinius erythrophthalmus) inhabit

this pool and might impair the population Pool 2

of dragonfly larvae. Bomb hole of about 3 m radius and a depth

Larvae of the following species were of about 1 m. Permanent pool, but varying

recorded within five years: Ischnura elegans, water level. Cattle can approach the water.

Coenagrionpuella, Erythromma najas, Aesh- Shallow litoral zone. No macrophytes at the

na Anax imperator, Libellula water edge meadow Galium cyanea, except grasses,

S. and quadrimaculata, Sympetrum flaveolum, palustre, Myosotis palustris very few

vulgatum, S. sanguineum. Juncus effusus. In every year the water sur-

of in In the cenosis larvae early summer face is completely covered with Ranunculus

I. is most Lemna. elegans abundant, followed by aquatilis and Filiform algae are

C. A. A. puella. cyanea, imperator, E. najas intermixed with the Ranunculus plants and

and S. with sanguineum decreasing num- form a dense layer on the water surface. 14 Notul. odonatol., Vol. I, No. I, pp. 1-16, June 1, 1978

Larvae of the following species of Odo- Conclusions

nata were recorded: Pyrrhosoma nymphula, The dragonfly fauna of small permanent

Erythromma najas, Ischnura elegans, Coena- meadow pools in Westfalia is relatively poor.

Aeshna Anax conditions of these bodies grion puella, cyanea, impe- Ecological water rator, Sympetrum sanguineum, S. flaveo- undergo drastic periodical changes, so that lum, Libellula quadrimaculata. Pyrrhosoma only eurytopic species may inhabit them,

most in larvae were abundant every year, forming rather typical cenoses of imagines, followed by Erythromma and Ischnura. with either Ischnura elegans, Erythwmma

few individuals of the other Only a species najas or Pyrrhosoma nymphula as dominat- were found. The weak occurrence of Ani- ing species, mainly depending on vegetation soptera might be due to the fact that the character. Although at most pools only

is de- of adult densely overgrown pool not easily cenoses Zygoptera are permanently

waters tected by migrant . present, these play an importantrole

Again the cenosis of the adults differed as reproduction reservoirs for anisopterous significantly from that of the larvae in that species as well. the Anisoptera were absent, except for some

Sympetrum individuals. This kind of habitat References - DUMONT, H.J., 1971, Bull. is not male Anax individuals - occupied by Annls Soc. r. ent. Belg. 107: 211-235; because of the lack of suitable Int. Revue resting FISCHER, Z., 1961, ges. Hydro-

places. biol. 46: 269-275; - JACOB, U., 1969,

The quantitative aspect of the cenosis Faun. Abh. Mus. Tierk. Dresden 2: 197-

of adults reflects the numbers of larvae: P. 239; - KREUZER, R., \940, Arch. Hydro-

nymphula is always most abundant, fol- biol. (Suppl.) IO; 359-572; - MUNCH- lowed by E. najas and I. elegans. In late BERG, P., 1956,Arch. Hydrobiol. 52: 185-

E. - summer only najas and I. elegans are 203; RUDOLPH, R., 1918,Abh. Landes- present. This cenosis cannot be classified in mus. Naturk. Munster 40 (in press). the terms of JACOB (1969). Received March 9, 1978