The Jailer of Midges

Lords-and ladies, Wild arum, Cuckoo-pint (Arum maculatum) (1) or Cluas chaoin in Irish is a May wildflower that likes woodlands and shady areas.  It is a plant of extraordinary interest because of its unusual method of attracting pollinators.  In fact, it relies mainly on one pollinator to carry pollen from one plant to another.  This is a midge called Psychoda phalaenoides. Females of this species lay their eggs on cow dung. 

Wild arum (1)

A close look at the plant under discussion reveals a spike called a spadix surrounded by a green cloak called a spathe. (2) This columnar spike is purplish in colour and is club shaped.  When this emerges a smell of cow dung can emanate from it.

Wild arum (2)

The midges mentioned are attracted by this smell and when they come to investigate in the lower part of the spathe they slip on its oily surface and fall into a chamber at the base of the plant.  They are trapped here because they cannot get a grip on the slippery surface of the sides and tiny hairs which are directed downwards prevent them from escaping.

The pollinating midges are held captive for two nights.  Then the hairs wither and the slipperiness on the spathe disappears so that they can climb out. By this stage they are covered in pollen from the male flowers and the chances are that they will visit another plant, be trapped again and deposit this fertilising pollen. 

The spadix and spathe then collapse and bright orange to red poisonous berries are formed.  These are eaten in the autumn by pheasants, blackbirds and thrushes. (3)

All parts of the plant are toxic, and the stem contains a sap which is a skin irritant.

Wild arum (2)

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