Temporal and spectral description of an additional signal type of male treehoppers

Animals vary in the complexity and size of the signal repertoire used in
communication. Often, these behavioral repertoires include multiple signal
types for the same process, for instance, courtship. While courting, males
of plant-feeding treehoppers (Hemiptera: Membracidae) perform plant-borne
vibrational signals with a frequency-modulated whine and a series of
pulses. Here we describe an additional signal type in the repertoire of
male Enchenopa treehoppers and compared it with other male and female
signals to explore its origin and function. We collected Enchenopa
binotata nymphs in meadows and forest edges in Wisconsin, USA, and reared
them to maturity. We did laser vibrometry recordings of the spontaneous
signaling bouts of adult males and found that the additional signal is
very common as two-thirds of males produced it. This signal substantially
differed in temporal and spectral features from the main male signals: do
not have pulses 25% of the times, and it has a shorter duration. We then
compared male signals to the female duetting responses. Treehopper females
selectively respond to males, which leads to duetting and mating. We found
that similar to the female response, the additional signal is performed
immediately after the first main male signal and is not modulated in
frequency. These similarities suggest that the additional signal might be
a female-mimic signal that males incorporated from listening to females.
However, experimental tests are required to explore its origin and
function. Overall, our findings highlight the diversity in the behavioral
repertoire that animals may use in for reproduction.