Question

Describe the alimentary canal of a cockroach and its interaction with mankind.

Answer 1

• The alimentary canal present in the body cavity of cockroach is divided into three regions: foregut, midgut and hindgut.
  
• The mouth opens into a short tubular pharynx, leading to a narrow tubular passage called oesophagus. This in turn opens into a sac like structure called crop used for storing of food.
• The crop is followed by gizzard or proventriculus. It has an outer layer of thick circular muscles and thick inner culicle forming six highly chitinous plate called teeth. Gizzard helps in grinding' the food particles.
  
• The entire foregut is lined by cuticle. A ring of 6-8 blind tubules called hepatic or gastric caecae is present at the junction of foregut and midgut, which secrete digestive juice.
• At the junction of midgut and hindgut is present another ring of 100-150 yellow coloured thin filamentous Malphigian tubules. They help in removal of excretory products from haemolymph.
• The hindgut is broader than midgut and is differentiated into ileum, colon and rectum. The rectum opens out through anus.
  

Cockroaches interact with mankind by thriving in and around their habitat. They are considered pests because they spoil food and contaminate it with their smelly excreta. They can transmit a variety of bacterial diseases by contaminating food particles.