A Study On Staphylinids Inhabiting Dead Pine Trees Caused By Bursaphelenchus Xylophilus And The Chemical Information Communication Mechanism With Host

With the generalization of "natural forestry" concept and decrease of disturbing onecosystem, dead standing trees and rotten woods increased gradually in the forest. Forest insectpopulation structures changes corresponding to forest resource structure variation. The numbersof“decomposers”feeding on dead standing trees and secondary pests damaging weak treesincreased. Many populations had the habit both “decomposing”and “damaging”, such aslong-horned beetles, bark beetles and snout beetles, which have become an important factorthreatening forest resources security. Commensalism organisms were taken as carriers bringingthe entomopathogens to control pests, and which was a new method of biological control withrapid development in recent years. Staphylinids inhabiting dead pine trees were the symbioticgroups of trunk borers. In this paper，population composition survey and niche analysis ofarthropods under the barks of dead pine trees caused by Bursaphelenchus xylophilus were used toevaluate the potential of staphylinids as carrier insect controlling secondry pests of pine trees.Meanwhile, taking the dominant rove beetle species, Homalota sp. as an example, its biology andchemical information communication mechanism with host were also studied to explore newapproach for using staphylinids resources. The main research contents and results are as follows:1. The populations of the arthropods under the barks of the dead pine trees belonged to27species,17families,7orders and3classes. Among which, the dominant species were ofPoduridae, Staphylinidae, Muscidae, and Scolytidae, the abundant species were of Cheyletidaeand Cerambycidae, the common species were of Bethylidae, Bothrideridae, Braconidae andCurculionidae, and the rare species were of Formicidae, Nitidulidae, Thripidae, Histeridae,Labiduridae, Elateridae and Cleridae.2. The Staphylinidae species had the broadest niche width. The values of temporal, spatialand temporal-spatial niche overlapa and of niche similarity proportion between Staphylinidae andScolytidae, Cerambycidae were higher than those between Staphylinidae and other species. Thissuggested that there existed the highest spatial and temporal encountering probabilities and themost obvious following performance between the Staphylinidae species and the main boringinsects such as the species of Scolytidae and Cerambycidae. Staphylinidae species have greatpotential for development and utilization as a carrier insect.3. The dominant species under the barks of the dead pine trees was Homalota sp.(Staphylinidae), which belongs to Genus Homalota, Subtribe Homalotina, Tribe Homalotini (=Bolitocharini), Subfamily Aleocharinae, and it is a new record genus and species inChina.4. Morphological characteristics and bioecological characteristic of Homalota sp.werestudied and larva was divided into three instars. Homalota sp. is saprophagy and carnivorous and likes feeding springtails, young maggots and young larvae of long-horned beetle. When feelingvery hungry, it also feeds on larvae of Scolytidae, Curculionidae, Elateridae, Formicidae,Labiduridae. We have not found that they preyed on living organisms in the course of experiment.Diel activity patterns of Homalota sp. adults were observed in laboratory and the result suggestedthat there existed two activity peak hours:8:00~11:00am and20:00~22:00pm.5. Host selecting behaviors of Homalota sp. adults were tested in laboratory using Y tubeolfactometer and the result showed that there were significant selectivity for substrates fromdifferent fallen time timbers. The response of Homalota sp. to substrate B (phloem with fungus)was the strongest and there was no significant difference between male and female adults.Electrophysiological response of Homalota sp. to host volatile were tested by GC-EAD analysis.The males were sensitive to (+)-a-longipinene and EAG response value was4mv, while thefemales were sensitive to clovene and longicyclene, EAG response values were0.8mv and3.4mv respectively.6. By comparing GC chromatograms among6solid phase microextraction fibers coatingdifferent materials, we obtained the optimal fiber for extracting Homalota sp. host volatiles.Host volatiles were detected and87chemicals were found by GC-MS analysis. Terpenecompounds (accounting for93.00%of the total content) occupied the main constitution, whichwere identified mainly including such chemical compounds as alpha-pinene (28.31%),longifolene (16.04%),1-caryophyllene (8.76%), beta-pinene (8.53%), d-Limonene (6.18%),camphene (5.61%), longicyclene (3.01%), isolongifolene (2.4%), alpha-caryophyllene (1.97%),(+)-4-carene (1.91%),(+)-a-longipinene (1.59%).7. Continuous monitoring of host volatiles were carried out and the results suggested thattemperature was the main factor affecting their quantity and composition. The numbers of hostvolatiles were gradually reduced and the relative content of various compositions also changedsignificantly with the temperature falls. The (+)-a-longipinene, clovene and1-caryophyllenepresented a trend of reducing afer rising at first, the longicyclene and longifolene overall showeda trend of rise. By analyzing relative content variation and alluring results in the wild, it can bededuced that (+)-a-longipinene and longicyclene were likely to be the lure compositions forHomalota sp. The wild bait-wood alluring showed that Homalota sp. adults appeared under thebark of the dead pine trees after cutting down20days. Thereafter, the species and numbers ofrove beetles were gradually increased and got fastigium during the period from32days to41days, which was concordant with the variation tendency of volatiles quantity and composition.