The polyphagous shot hole borer (PSHB),Euwallacea sp.,was first detected in 2003 in Los Angeles County,Califoia,USA.Recently,this invasive species has become a major pest of many hardwood trees in urban and wildland forests throughout southe Califoia.PSHB is nearly identical in morphology and life history to the tea shot hole borer (TSHB),Euwallaceafoicatus,an invasive pest of hardwoods in Florida,USA and many other parts of the world.However,molecular studies have suggested that the taxa are different species.We conducted morphometric and chemical analyses of the phenotypes of Euwallacea sp.collected in southe Califoia (Los Angeles County) and E.foicatus collected in Florida (Miami-Dade County).Our analyses indicated that PSHB has 3 larval instars.The third larval instar was separated from the first 2 instars by head capsule width with 0 probability of misclassification.The body length,head width,and pronotal width of PSHB adult males were significantly less than those of females.Head width and pronotal width of female PSHB were significantly less than those of female TSHB.In contrast,body length,and ratio of body length to pronotal width of female PSHB were significantly greater than those of female TSHB.However,females of these 2 species could not be separated completely by these 4 measurements because of the overlapping ranges.Cuticular hydrocarbons detected in both species were exclusively alkanes (i.e.,n-alkanes,monomethylalkanes,dimethylalkanes,and trimethylalkanes).Cuticular hydrocarbon profiles of PSHB males and females were similar,but they both differed from that of TSHB females.Cuticular hydrocarbons of PSHB were predominantly inteally branched dimethylalkanes with backbones of 31 and 33 carbons,whereas cuticular hydrocarbons of TSHB females were dominated by inteally branched monomethylalkanes and dimethylalkanes with backbones of 28 and 29 carbons.Multiple compounds within these classes appear to be diagnostic for PSHB and TSHB,respectively.