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Friday, 28 December 2018

Feeding Adaptations in Insects

 Insects feed on a variety of foods. Grasshoppers and cockroaches feed on solid food. Moths and butterflies are fluid feeders, sucking nectar from flowers. Mosquitoes pierce the skin of animals in order to suck blood. Houseflies cannot take in solid food. They externally digest solid food into a liquid form and then suck it up.

    All insects have basic mouthparts which are modified according to the food they eat. The mouth of the grasshopper consists of several parts, each of which has a long proboscis for sucking up liquid. The mandibles and Labrum are reduced because they are no longer needed. When the proboscis is not in use, it is coiled up. It is uncoiled by pumping blood into it from the body cavity.

   Like the butterfly, the mosquito takes in liquid food only has mouthpart modified into a proboscis. The male mosquito feeds on nectar and plant juices. Its proboscis is used for sucking only. The female feeds on the blood of animals. Its proboscis is modified for piercing and sucking. The proboscis consists of four long sharp stylets, modified from the mandibles and maxillae for piercing through skin. The Labrum is deeply grooved. When the Hypopharynx is fitted closely against it, it forms a channel along which fluid food is pumped. The Hypopharynx also contains a salivary duct which injects saliva into the wound. The saliva prevents the blood from clotting and also causes itching and swelling of the skin. The labium is sheet like and holds the different parts of the proboscis together.

   In the housefly, the proboscis, formed from a modified labium, is a sponge like organ composer of two halves, called labella (singular: labellum) Each labellum has numerous fine food channels which join to form a central proboscis canal. When feeding, the proboscis is extended by blood pressure and pressed on the food. If the food is solid, saliva is secreted on it. The saliva contains enzymes which digest the food extra cellularly and change it to a liquid. The liquid food moves up the fine channels in the labella by capillary action and is then sucked into the alimentary canal.  
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