Cercobrachys minutus (Tshernova, 1952)
Brachycercus minutus Tshernova, 1952: Russev, 1968: 295; Russev et al., 1984: 63.
Order Mayflies (Ephemeroptera)
Family Small square-gilled mayflies (Caenidae)
Conservation status: in Bulgaria: Critically endangered CR [A2a; B1ab(iv); D; E].
General distribution. Belgium, the Netherlands, Denmark, Northern Germany, Poland, the Baltic countries, the Czech Republic, Slovakia, Hungary, Bulgaria, Romania (the Danube Delta), the Ukraine, European Russia, the Far East (Amur River).
Distribution and abundance in Bulgaria. Known from the Danube at Lakat Island and Svishtov and from the Tundzha River above Yambol and above Elhovo [1, 2]. The species was found between 1958 and 1966, always in few specimens. It has not been recorded in the Bulgarian Danube section since 1973 . It was not found also during the investigations of Tundzha in 1981  and 2006 [unpublished data].
Habitats. A psammophilous species whose nymph inhabits the sandy bottom of large lowland rivers .
Biology. An extremely rare species, hence its biology is almost not studied at all.
Similar species. Brachycercus harrisella, from which it differs with the absence of cone-like spikes on the head of the nymph.
Negative factors. Degradation of the habitats caused by man. Extraction of inert materials from the bottoms of rivers as well as their pollution with waste waters.
Conservation measures taken. None.
Conservation measures needed. Prevention of the pollution of the middle and lower courses of larger rivers. Restoration of the habitats of the species where it has occurred in the past.
References. 1. Russev, 1968; 2. Russev et al., 1984; 3. Russev, Uzunov, 1991a; 4. Janeva, Russev, 1985.
Author: Yanka Vidinova