Reed beds are extensive aggregations of herbaceous monocotyledons that accumulate where the ground is more or less permanently damp or wet and where the waterside gradient is shallow enough for their expansion away from the water, they often become established along river and lake margins where they are restricted to the open water if the bank is too steep for their expansion, in which case they are of more limited interest to the coleopterist, otherwise they grow so densely that all other plants are excluded from the immediate area although the margins may display lush and diverse plant communities. Reed beds are defined as wetlands that are dominated by the common reed, Phragmites australis, and where the ground is saturated or flooded for most of the year; reed swamps are normally flooded with at least 20cm of water during the summer. From a botanical point of view reed beds are generally of little interest but otherwise they are teeming with wildlife and should be a magnet for coleopterists. They occur naturally across much of the U.K., especially in coastal areas generally and low-lying
areas in the east and southwest, and are often planted to protect shores and banks from erosion or to help keep the water in a good condition. Reed beds are very resilient; they may become established from seed or from drifting fragments of plants in waterways, but once mature the plants spread by rhizome growth that extends both horizontally and vertically through the soil forming dense and impenetrable masses. During the summer the green ariel parts provide the rhizomes with oxygen and food while during the winter the hollow dead stems provide oxygen but are also a haven for overwintering insects of all kinds. Within established bank-side reed beds the leaf-litter is generally so deep and dense as to act as a mulch, conserving moisture and preventing other plants from becoming established. Depending on the waterside gradient and soil-type they generally begin at the water edge, or extend a short way into the water, and continue for few tens of metres. A casual inspection might suggest a lack of beetles and the obvious thing to do is sweep the margins, this will produce a varied list of species, especially in warm weather, including various Coccinellids, Stenus, Demetrias, Donacia, Psammoecus, and Anthocomus etc. as well as a whole range of other
species associated with other waterside plants e.g. Prasocuris and Phaedon. This is also a good way to obtain members of some families seldom seen in general e.g. leiodids and a few choice weevils etc. But beyond this rather obvious approach it pays to look a closer. Despite being difficult it is generally possible to make a path through the reed bed to the water edge, and in doing so it soon becomes obvious that the ground becomes increasingly damp, at first solid underfoot then soft and wet and finally waterlogged. This moisture gradient is a useful thing to learn to work with as once one is familiar with what kind of fauna occurs at which level it is easy to work new reed beds in a quick and efficient way. Fortunately the deep litter is rather comfortable to sit or lie down on, and this makes sampling much easier; spending half an hour sitting and observing the reed stems will usually produce a few specimens e.g. many carabids and staphs will be seen to climb them, but to really find out what is there it is necessary to search among the litter. Pitfall trapping is very successful, especially when these are baited with fish etc., and leaving carrion, exposed or in traps, can be very rewarding, as can searching under debris, but during a one-off visit to remote sites when time is limited it is necessary to more active. The best way to sample a reed bed, given limited time, is to lie down so that the ground can be examined carefully and comfortably, and to scrape away an area of litter so that the soil is exposed, no more than one or two square feet need be cleared as it will be around the edges that will be of most interest. After the initial clearance a few staphs and carabids will be exposed and after a few minutes they will run for cover. Over the next five minutes a few more will leave the soil and run and that will be that, but the real interest should be around the margins of the cleared soil. Carefully working these margins back and exposing new soil will produce a constant stream of specimens, and with patience more will appear after a few minutes i.e. those displaying thanatosis, when the ground seems to be devoid of specimens it can be flooded in sections from a bottle and more will appear, in this way various weevils and small carabids may start to move. This process can be continued from the water edge to the limits of the reed bed and will produce many interesting specimens, and it helps to be aware that some rare species might be present and mistaken for more common ones e.g. Paradromius linearis is common everywhere but the very local and rare
Other insects, such as the Water Stick Insect (Ranatra linearis) can be found in reedbeds.
P. longiceps occurs only in reed beds and would be a significant find. Many species occurring in other habitats will also be found to be common in reed beds e.g. this is the only situation we have found the fascinating Deinopsis erosa (Stephens, 1832), and Hygronoma dimidiata (Gravenhorst, 1806) is often present along the waterline in large numbers. Some will only be found in reed beds e.g. Demetrias imperialis, and searching along the south coast one may be lucky enough to find such gems as Drypta dentata. Our local reed bed, sited between the river Colne and a housing estate in Watford, is often teeming with various common species of Stenus; all the usual suspects but also a healthy population of the very local S. nitens, discoveries such as this involve many hours of work, both in the field and in the lab, but are so very satisfying. As with many habitats reed beds have a basic fauna that will be present wherever they are worked e.g. a host of common carabids and staphs and along the waterline many hydrophilids will be abundant. This means that a level of expertise will soon develop e.g. species of Anacaena will always be seen along the waterline or among saturated litter and after a while the larger and more convex form of A. globulus will be obvious, and when the paler and distinctively marked A. bipustulata occurs it will be recognized immediately as something different. Reed beds are also an excellent habitat to obtain specimens in abundance that will test ones powers of identification; there will be many Cercyon, Phalacrids, Atomaria and other cryptophagids, small hydrophilids, staphs, histerids and leiodids etc. etc. that will greatly widen ones appreciation of many of the families. Taking home samples of litter for extraction can be done profitably at any time of year and so when things are otherwise quiet such samples may produce Hydraenids and Ptilids in abundance as well as the odd Hydrochid and dytiscid and a whole host of other species.
Common Reedbed species
Bembidion lunulatum (Geoffroy, 1785)
Agonum marginatum (Linnaeus, 1758)
Protapion assimile (Kirby, 1808)
If You're Lucky
Dytiscus dimidiatus Bergsträsser, 1778
Donacia sparganii Ahrens, 1810
Bagous lutulosus (Gyllenhal, 1827)
Lixus iridis Olivier, 1807