Morphological Characteristics And Symbiotic Fungi Species Of Three Ambrosia Beetles

The ambrosia beetle is an important kind of forest tree pests.In recent years.Euwallacea fornicatus Eichhoff.Scolytoplatypus raja Blandford and Platypus sp.have seriously endangered Camellia chekiangoleosa Hu,Litchi chinensis Sonn.and Ficus microcarpa L.f.in Yunnan,Fujian and other places in China,resulting in debilitating growth or even dead of their host.In order to clarify the distinguishing characteristics of three ambrosia beetles and the species of symbiotic fungi,we observed the morphological characteristics and the microstructure of ambrosia beetles using stereomicroscope and scanning electron microscopy,and the main symbiotic fungi of three ambrosia beetles were isolated and identified by the tissue separation techniques and combination of morphological-molecular systematic analysis.The main results were as follows:1.The main distinguishing features of three ambrosia beetles' adults were clarified.(1)The male frons of the S.raja has frontal hairs only and no marginal hair.Prosternum with tw o tubercles anteriorly,and anterior to them a pair of tapering processes diverging at an angle of about 120°.and there are 6-9 spines between the odd numbered interstriae on the elytral declivity;the front and middle parts of the female's pronotum is inycangia.(2)The summit of the male of Platypus sp.was clearly elongated with a pair of oblate long odontoids;the pronotum of female has a heart-shaped mycangia.(3)The males of E.fornicatus have a length of 1.5-1.8mm,and the frons is very flat,the middle part is smooth and bright,no engraved spots and hairs;The dorsal view of the female pronotum is shield-shaped,the leading edge is rounded and the trailing edge is slightly flat in lateral view,the rear edge of the elytral has a slightly sharper edge.2.The microstructure of mycangia of two ambrosia beetles was clarified.(1)The S.raja's mycangia is located on the anterior middle of the pronotum of the female adult.It is an oval depression with spiky hair on the edges and inside,and it is filled with irregular substances and fungal spores.(2)The mycangia of the Platypus sp.is located on the pronotum of female and male adults.The female mycangia is heart-shaped and contains 10017 chambers.The male mycangia is irregular and contains 4±1 chambers.sometimes without chambers,have a tapered hair inside the edge of each chamber and a structure similar to that of the brain.3.The species of symbiotic fungi of the tlu-ee ambrosia beetles were clarified.The symbiotic fungi of S.raja and Platypus sp.are Ophiostoma sp.The symbiotic fungi of E.fornicatus have certain differences between different hosts in different regions.In Kunming,Yunnan,the symbiotic fungi of E.fornicatus are Fusarium cf.solani and F.ambrosium,but the dominant species in different hosts is different.The symbiotic fungi on the F.microcarpa is F.cf.solani,and the symbiotic fungi on the P.acerifolia is F.ambrosium;Geosmithia sp.and Fusarium sp.were found on the L.chinensis of Zhangzhou,Fujian,different from the symbiotic fungi of Kunming,Yunnan.By observing the morphological characteristics of the three ambrosia beetles,the main distinguishing characteristics of them were clearly identified,which was favorable for their rapid identification.At the same time,by studying the microstructure of mycangia and the types of symbiotic fungi,we can provide references for further study on the symbiotic fungi carrier and symbiosis mechanism.