FISH detection of Wolbachia genes on the chromosomes of Callosobruchus chinensis strain jC^Aus. (A) Metaphase chromosomes of a male insect. X and Y indicate X chromosome and Y chromosome, respectively. Note that C. chinensis is male-heterogametic with a karyotype of 2n = 20, XY. (B) Metaphase X chromosomes from different preparations, with yellow line indicating the position of centromeres, magenta, areas indicating Wolbachia gene signals; and green indicating insect chromosome signals. Bars, 1 μm.