Ambrosiophilus sulcatus is variable in body length, the degree of bisulcation of the elytraldeclivity and in the size of the declivitalgranules, but all specimens form a continuous spectrum of variation. Specimens from India and China (Fujian) are larger, more strongly bisulcate and have slightly larger granules than specimens occurring further south (Myanmar and Vietnam).
The type specimens of Xyleborus sinensis, X. sulcatulus, and type images of X. sulcatus were directly examined. The specimens differ in size (2.8 mm X. sulcatulus, 3.0 mm, X. sulcatus, 4.2 mm X. sinensis), the depth of the elytraldeclivitalsulci, and in the degree development of interstrialgranules. Additional non-type specimens were also examined. We found that size, depth of the declivitalsulci, and development of interstrialgranules formed a continuum of variation.