Polytene nucleus of the F1 hybrid of B. dorsalis s.s . × B. carambolae. Note the perfect synapsis along the parental homologous chromosomes. Arrow indicates the polymorphic inversion found in the distal part of 2R chromosome arm in the Saraburi colony of B. dorsalis s.s. The chromosome tips are indicated; h indicates pericentric heterochromatin. Scale bar represents 10 μm.