Sex Pheromone in the Aphid <Emphasis Type="Italic">Megoura viciae</Emphasis>

THE adult egg-laying females (oviparae) of most holocyclic aphid species bear on their swollen hind tibiae circular plaques or tubercles which taxonomists variously refer to as sensoria, pseudosensoria, or pseudorhinaria. It has been suggested that they aid the ovipara in fixing her eggs to the host plant¹, that they are sensory receptors², or that they produce a sex pheromone which attracts the males^3–5. Pettersson⁶ has advanced preliminary evidence for the latter function in a species of Schizaphis. Recent studies have shown that these structures (Fig. 1) in Megoura viciae Buckton do indeed secrete a sex pheromone and, moreover, that striking changes in the daily pattern of pheromone release occur as the female ages. In this article these pseudosensoria will be referred to as “scent plaques”, an appropriate term first used by Stroyan⁷.