It was studied somatic section of trunk nervous system at 218 specimens (23 species, 20 genera, 11 families) of Diptera in connection with innervating region (pectoral and abdominal musculature) and body segmentation. It is established high degree of variability of ganglion number (1-7) in abdominal nervous chain. The pectoral ganglia are merded to unified syn-ganglion at the studied Diptera. Number of free abdominal ganglia varies between 1 and 6. It is established attended dependence of degree of nervous system oligomerization, pectoral and abdominal musculature and body segmentation.