| dc.description.abstract | Initial investigations into bioacoustics of Cicindela spp.
(Cicindelidae: Coleoptera) were designed to establish the
systematic usefulness of acoustic variables, the possibility of
auditory communication, and lay foundations for future studies of
acoustic behaviour of the family.
Groups were statistically compared using variables derived
from photomicrographs of plectra as well as oscillograms and
frequency spectrograms of recorded stridulations.
The noise-like character of tiger beetle stridulations
necessitated a new method of comparing stridulation frequency
spectra averages: discrete frequencies from the peak-pick
procedure of a Nicolet lOOn mini-analyzer were compared.
The plectrum consists of a field of posteriorly oriented
spines located ventrally at the elytral apex. Plectra characters
show trends towards sexual dimorphism and are related to body
size and habitat. Among plectra/elytra characters, plectrum field
size and shape show the most promise as taxonomic characters.
Stridulations, produced by a two-stroke cycle, consist of 1
to 9 low intensity buzzes (modes), signal mean 49.0 dB at 3 cm
(audio range), with an average duration of 0.65 seconds.
Cicindelids emit signals of broadband frequency, between
approximately 20 Hz and 50 kHz, with significant energy in both
audio and ultrasonic ranges.
Although stridulations, for the most part, showed no sexual
differentiation, species differences were quite apparent. Signal
timing and amplitude parameters were based on body size, plectrum
structure, phylogeny, and habitat. Stridulation frequency was
based on phylogeny and may be related to specific stridulatory
behaviour and structure of the pars stridens. Acoustic characters
appear to show limited promise as useful taxonomic characters.
Temperature at stridulation does not appear to affect
stridulatory rates. Evidence suggests that stridulatatory
behavior is linked to specific optimal temperatures.
Tiger beetles stridulate spontaneously or when subjected to
heated, lighted, or crowded conditions. In contrast to most
coleopterans, tiger beetles do not stridulate in response to
mechanical stimulation, a behavior associated with a disturbance
function. This togther with a relatively ordered stridulatory
structure, and initial behavioral observations suggest a
territorial and/or calling function of cicindelid stridulations. | |
