Strange moss-like balls are formed on the wild Dog Rose when the small wasp Diplolepsis rosae lays eggs in the leaf buds or even the stem. The presence of the devloping larvae stimulates a proliferation of abnormal narrow leaves which are commonly called Robin’s Pincushions of Bedeguar Galls.
The following is an account, written almost exactly a hundred years ago, describing this type of gall. You’ll notice that the Latin name of the wasp has changed since that time. The author, E. W. Swanton [Member of the British Mycological Society, and of the Association of Economic Biologists; Curator of the Educational Museum, Haslemere; author of “Fungi and How To Know Them“] uses wonderful language to describe the phenomena and I particularly like his anthropomorphological reference to the wasp having made ” an error of judgement” !
Rose leaves attacked by Rhodites produce some of the most attractive of British galls. One of these is the well known and universally admired gall popularly known as “Robin’s Pincushion”, “Moss Gall”, or “Bedeguar Gall”. The curious word “Bedeguar” is said either to be derived from the Persian or Arabic bãdãwar, “wind-brought,” or to be a compound of the Persian bãd, “wind” and the Arabic ward, “rose.”
When occurring on the Sweet Briar this gall is sometimes spoken of as the “Sweet Briar Sponge”. It arises from the attack of a leaf bud in spring by the female Rhodites rosae. According to Pavlasky, she pricks the bud carefully in three distinct places, causing the three rudimentary leaves to develop, not as normal leaves, but into the curious production so well known to botanists. The “moss” is leaf but with little parenchyma between the fibro-vascular bundles.
The gall is usually large, but occasionally, through an error of judgement on the part of the wasp, or more probably through interruption during the pricking operation, an abortive gall arises, a much smaller structure seated on a developed leaf. This gall is at its best in the latter part of July and early in August. It occurs chiefly on small and weakly bushes.
As the male is rare, Rhodites rosae is doubtless a parthenogenic species. The galls were used medicinally in olden times, and less than a centuary ago the farmers of the Harrogate district used them for an infusion to cure diarrhoea in cows. Old Réaumur said that the smell of Bedeguar galls is attractive to cats.
Swanton, E. W. (1912) British Plant Galls – A classified textbook of cecidology, Methuen & Co. Ltd, London.
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