First description of substrate-borne signals emitted by males of Macrolophus pygmaeus

Vibrational communication is widespread in insects where it represents the main communication channel for more than 70% of the families. The sexual behaviour of numerous species is charecterized by the use of substrate-borne signals. In Heteroptera the vibrational communication has been deeply investigated in the Pentatomidae family, but very little is known about other families, including the Miridae for which olfaction has always been considered the main intraspecific communication channel. Macrolophus pygmaeus (Rambur) (Hemiptera: Miridae) is an economically relevant species for the biological control of several pests in the Mediterranean region. In Europe, it is commercially reared for biological control of whiteflies Trialeurodes vaporariorum (Westwood) and Bemisia tabaci (Gennadius) (Sternorrhyncha: Aleyrodidae) in tomato greenhouses. In the present study we investigated the ability of M. pigmeus males to produce substrate-borne signals during mating behaviour. Two different experiments were carried out using a laser vibrometer. The first one aimed to record the vibrational signals produced by a male on a tobacco leaf in three situations: male alone, male with a female and male with another male. The second experiment used a minishaker to playback male signals to evaluate if they affect the behaviour of conspecifics. The results showed that males of M. pygmaeus can emit two different substrate-borne signals that we onomatopoeically called “roaring”, a long broadband signal produced by a continous oscillation, and “yelping”, a train of short repeated signals with harmonic structure. We also found that the playback of “roaring” modifies the behaviour of listening? (receiver?) males, in terms of increased locomotion. Yelping, instead did not induce any significant variation either in listening males or females. This signal, however, was always recorded in test 1 before mating attempts. This suggests that yelping would function as stimulus of male acceptance from a female. In conclusion, this is the first report of the use of substrate-borne vibrational signals by a Miridae species for mating behaviour and a contribution to better understand its reproductive biology