Spalangia endius, a pupal parasitoid of tephritid flies, has a karyotype of n=4, the lowest haploid chromosome number ever recorded for a pteromalid. This was determined by examining mitotic cells of the neuroganglia of male pupae. A diploid chromosome number (2n)=8 was also determined from the neuroganglia of female pupae. The diploid mitotic karyotype is comprised of 4 metacentric chromosome pairs.