(A–Q) Transmission electron micrographs of regions I, II and III of the mature spermatozoon of Tergestia laticollis. Scale bars = 0.2 μm. (A–F) Sections in the anterior extremity of the spermatozoon. (A–B). Longitudinal (A) and cross-sections (B) in the anterior extremity of the spermatozoon with only the centriole of axoneme 1 (Aae1). (C) Cross-section in the anterior extremity of the spermatozoon with only one axoneme (A × 1). (D) Cross-section in the anterior extremity of the spermatozoon with axoneme 1 and three cortical microtubules. (E–F) Cross-section in region I of the spermatozoon with axoneme 1 and the centriole of axoneme 2 (Aae2) (E), then the two axonemes (A × 1 and A × 2) (F). (G–K) Cross-sections in region II of the mature spermatozoon showing the two axonemes, an increasing number of cortical microtubules up to 36 in (K), and the external ornamentation of the plasma membrane (Eo) and spine-like body (Sb) (K). (L–Q) Cross-sections in region III of the mature spermatozoon showing only two axonemes and a row of 26 cortical microtubules (L), 25 (M), the appearance of the first mitochondrion (M1) (N). Then, the disappearance of the first mitochondrion (O), disappearance of axoneme 1 (Pae1) and the disorganization of axoneme 1 (P). (Q) Cross-section in the extremity of region III showing only a row of 13 cortical microtubules and axoneme 2.