http://www.eje.cz tein, TRA F , which combines with TRA2, a non sex-specifi c protein, generating the TRA/TRA2 complex protein. This protein complex regulates dsx splicing in the female mode to produce DSX F , which directs female embryonic development. In XY embryos that do not have the SXL protein, both tra and dsx genes produce male-specifi c proteins, TRA M and DSX M , which induce embryos to develop as male fl ies (Baker & Wolfner, 1988; Burtis & Baker, 1989; Hoshijima et al., 1991; Salz & Erickson, 2010). Sex determination cascades of other insects do, however, seem to be different from that of Drosophila. In tephritid insects for example, the Sxl genes identifi ed from Ceratitis capitata and Bactrocera oleae do not function in sex determination, although their Sxl sequences are highly similar to that of Drosophila (Saccone et al., 1998; Lagos et al., Identifi cation and characterization of doublesex from the pumpkin fruit fl y, Bactrocera tau (Diptera: Tephritidae

The filamentous spermatozoa of scale insects (Hemiptera) are highly modified compared with those of typical insects. Here, we investigate the morphology of the testes, sperm bundles, spermatozoa, and spermatogenesis of the winglessKerria chinensis(Mahdihassan) (Hemiptera: Kerriidae), a shellac-producing scale insect. Each testis contains two antiparallel groups of several hundred syncytial sperm bundles. In each spermatocyte cyst, 16 primary spermatocytes divide via inverted meiosis, resulting in 16 quadrinucleated spermatids, each having two euchromatic and two heterochromatic nuclei. During spermiogenesis, each spermatid produces two spermatozoa protruding out of the spermatid close to the two euchromatic nuclei and their tails then grow in opposite directions. In each cyst, the 32 spermatozoa form two sperm bundles lying in an antiparallel direction oriented to different ends of the testis. Each spermatozoon has three distinct regions, an apex, a filamentous region and a tail. The spermatozoa have long thread-like nuclear cores that occupy about one-fourth of the sperm body length, located primarily in the posterior half. At the anterior end of the spermatozoon is a translucent, swollen vesicle and a distal, densely-stained structure; a putative acrosome of a type not previously reported in the spermatozoa of scale insects.