Stridulatory Signals And Structures Of Bark Beetles And Its Application To Automated Species Identification

Bark beetles in Scolytidae are the very important forest pests, classification of which is the basic of research and prevention. However, the bark beetles, distributed in many species, are small and some are familiar in appearance, which makes the classification difficult. So far the methods of classification of bark beetles are mainly made use of the features of appearance, physiology and genetics but the bioacoustics classification has not been reported. This paper shows the research on the bioacoustics of Dendroctonus valens, Dendroctonus armandi, Tomicus yunnanensis,Tomicus brevipilosus and Tomicus minor specially including three aspects: find the differences of stress stridulation of five bark beetle species in time and frequency domain; research into the automated identification of the five bark beetles by bioacoustics on the basis of the related techniques of speech recognition; describe and compare the location and appearance of stridulatory organs of Tomicus yunnanensis,Tomicus brevipilosus and Tomicus minor and prove the interspecific differences further by SEM. The results are as following:(1) Analyze time-domain including number of pulse groups and lasting time of pulse groups as well as frequency-domain including main peak frequency of five bark beetle species. The result was that the differences between the species in the different genus were obvious, whereas the differences between the species in the same genus were indistinctive.(2) The automated identification and classification system based on ANN and MFCC worked well, which the highest identification rates were 100% and the average identification rate was 88.8%, supplying a more convenient method to classification and identification of bark beetles. The results showed that identification rates of LPCC as a control were obviously lower than that of MFCC, just like the results in speech recognition.(3) The files of three Tomicus beetles from Yunnan were familiar and consisted of parallel ribs. The files on the right and left elytra had discrepancies, which were especially embodied in there being a area consisted of squamae between the file and the sutural on the right elytra but not on the left elytra, which resulted in the length of ribs on the left longer than that on the right. Otherwise, the ribs of the left elytral file were more intensive and deeper than those of the right elytral file. Thus, it was deduced that in the stridulatory process the left file took the main role and the right one was accessory. The ribs of male file were more intensive and deeper than those of female file.(4) The plectrums of three Tomicus beetles were consisted of numerous small cone-like structures. There were few differences between male and female beetles. Interspecific difference between the three species was remarkable: the plectrum of T. yunnanensis was consisted of one row of cone-like structures; the plectrum of T. brevipilosus was consisted of one to two rows of cone-like structures, usually two rows at the middle; the plectrum of T. minor, consisted of two to three rows of cone-like structures, was more unorderly. The difference can be another evidence to classify the three species.