Fig. 2

Determination of the sex ratio in tra-2 RNAi transgenic mosquitoes. a Pupal sex ratio among the progeny of 10 single-pair crosses (Crosses 1–10) between homozygous males and females of line 6. b Pupal sex ratio among the progeny of 10 single-pair crosses (M1–10) between male (M) offspring from Cross-1 and Cross-2 and Rock females. Dissection of testes allowed males to be classified into those with very few sperms (V), lower sperm density (L) and normal sperm density (N) in comparison with Rock males. V = between 4 and 45 sperm; L = between 109 and 304 sperm; N = more than 400 sperm. c Pupal sex ratio among the progeny of 10 single-pair crosses (F1–10) between female (F) offspring of Cross-1 and Cross-2 and Rock males. The transgenic mosquitoes used for the crosses in a, b and c varied between 3 and 9 days old. Numbers at the top of the columns show the ratios of males and females. A significant deviation from the 1:1 sex ratio in a Chi-square test is indicated by *P < 0.05 or *** P < 0.001. The symbol ♦ indicates crosses in which dead sperms were found in the spermathecae of living Rock females 23 days after insemination by M1–10 males. All the crosses produced at least 80 eggs per cross with hatching rates >80 %, except for family F3 with a hatch rate of 71.9 %. The details of hatching rates and statistical tests are presented in the Additional file 5