KEY TO THE EUROPEAN SPECIES OF BRACHYCAUDUS, SUBGENUS ACAUDUS (HOMOPTERA, APHIDOIDEA), WITH REDESCRIPTIONS AND A NOTE ON B. PERSICAE by H. C. BURGER Plant Protection Service, Wageningen Abstract A key is given to the 17 European species of the subgenus Acaudus Van der Goot. Three closely related species living on Caryophyllaceae are redescribed, viz., Brachycaudus (Acaudus) lychnidis (Linnaeus, 1758); Brachycaudus (Acaudus) klugkisti Borner, 1942; and Brachycaudus (Acaudus) populi (Del Guercio, 1911). Host alternation of Brachycaudus persicae (Passerini, I860) from Prunus to some Scrophulariaceae, was experimentally confirmed. Introduction The subgenus Acaudus Van der Goot, 1913 is a well-defined group of species, dis-tinct from the other Brachycaudus by the presence of a pair of semiglobular or mam-miform processes on the anterior part of the mesosternum (mesosternal processes) in apterae and larvae 1 ) (Hille Ris Lambers, 1956). Besides, a dark sclerotic dorsal shield is present in apterae viviparae. Keys to the genus Brachycaudus Van der Goot, 1913, were published by Remaudière (1952) and by Shaposhnikov (1964). Remaudière, in his key, treats ten Brachycaudus species from France, of which B. amygdalinus (Schout.) belongs to the subgenus Thuleaphis H.R.L., I960, and B. helichrysi (Kltb.) to the subgenus Brachycaudus. The other species mentioned all belong to the subgenus Acaudus. I consider B. semisubterraneus C.B. and B. persicaecola (Boisd.), and perhaps also B. mimeuri Remaud., to be synonyms of B. persicae (Pass.). B. lateralis (Wlk.) I consider a synonym of B. cardui (L.). Shaposhnikov, in his key, deals with 19 Brachycaudus species, two of which are Appelia species {cerinthis Bozh. and prunicola (Kltb.)); two, amygdalinus (Schout.) and rumicicolens (Patch), belong to the subgenus Thuleaphis (syn. Brevicaudus Shap.); and three, salicinae C.B., helichrysi (Kltb.) and spiraeae C.B., to the subgenus Brachy-caudus. The remaining species mentioned by Shaposhnikov fit into the subgenus Acaudus, but I do not include B. {A.) virgatus Shap. in my key, because too few samples are available and, therefore, my information about this species is not sufficiently reliable. In my key to Acaudus I add five more species, iranicus Davatchi & Remaudière, populi (Del Guercio), lychnicola H.R.L., jacobi Stroyan, and lamii (Koch). B. napelli *) Only in Brachycaudus lucifugus F. P. Müller the mesosternal processes are reduced or absent. z ) "rumicicolens" is misspelled for "rumexicolens". 99
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