An unusual population of Boyeria irene (Fonsc.) in Hérault, France (Anisoptera: Aeshnidae)

In July 1979 I found a strong population of B. irene on the R. Vis, near Soutayrol. Dep. Herault. France (G.S. VICK, 1980, Bull. amat. Ent. Soc. 39: 48-54). The river was moderately fast at this point, flowing over a rocky bed and heavily shaded by overhanging trees. The odonate fauna also consisted of Onychogomphus uncatus (Carp.), Cordulegaster b. boltoni (Don.) and Calopteryx virgo meridionalis Sel., but the lack of species diversity was compensated by the immense numbers of individuals, especially of B. Irene. Both forms of female were present, i.e, the so-called "normal" form with very short anal appendages (f. brachycerca Navas) and the type form with long appendages, which is usually considered to be rare (P. AGUESSE, 1968, Les Odonates de I’Europe Occidenlale, Masson, Paris). The two forms are very distinct; appendage lengths are about 2 and 6 mm respectively for the two forms. O.-P. WENGER (1959, Mill, schweiz. ent. Ges. 32: 304-311) showed that B. Irene larvae can be readily separated into the two forms by examination of the lengths of the cerei. Also P.- A. ROBERT (1958, Les libellules (Odonates), Delachaux & Niestlé, Neuchâtel), in his description of the larva, says ”les app. sup. (cerei) atteignent le tiers ou les trois-cinquièmes des cerques chez la 1 found separation of the female exuviae using this method to be very straightforward; if the cerei were appreciably less than half the length of the paraprocts the specimen was f. brachycerca, if they were appreciably more than half the length of the paraprocts the specimen was the "long appendage" form. No doubtful intermediate specimens were found.