The central nervous system of the cockroach consists of ventral nerve cord which extends from the sub-oesophageal ganglion ventral to the alimentary canal. It bears three thoradc and six abdominal ganglia. Spiracles are slit-like openings through which air enters inside the'respiratory system. Phallomeres are three chitinous structures that surround the male gonophore which help in transfer of the spermatophore from male cockroach to female cockroach. Ocellus is a simple eye that occurs in insects and other invertebrates. It typically consists of light-sensitive cells and single cuticular lens.