Solution:
Spiracles or stigmata are special valve containing tubules through which atmospheric air enters and escapes out during gaseous exchange in cockroach. Spiracles are 20 in number, out of these 2 pairs are found in
thoracic portion while rest 8 pairs are found in abdominal portion. Thoracic spiracles are somehow larger then abdominal spiracles. Peritreme, a ring like sclerite surrounds each spiracle.
