The karyotype of Toxorhynchites amboinensis consists of 1 metacentric and 2 slightly submetacentric pairs (2n=6). The average lengths of the metaphase chromosomes are: I=6.68 mm, and III=8.55 mm. Average arm ratios are: I=1.0000, II=1.034, and III=1.017. Somatic pairing is exhibited in all three pairs of mitotic chromosomes.