Piercing & sucking mouth parts in mosquitoes

Piercing & sucking mouth parts in mosquitoes:-
In mosquito, mouth parts are piercing & sucking type i.e. they are adapted for piercing the tissues of animal or plants to suck blood or plant juice.
The mouth parts consist of labium, labrum-epipharynx, hypopharynx, mandibles & maxillae.


Mouth parts:-
1. Labium:-
 The labium is modified to form a long, straight, fleshy tube called proboscis. It has a deep labial groove on its upper side. At the distal end of labium is a pair of small tactile labella which are reduced labial palps.
Function:-
The labial groove lodges all other mouthparts. During piercing, labella guides the mandibles & maxillae. The whole labium bends back to allow needle like mouthparts to go in the flesh.


2. Labrum-epipharynx:-
The labrum is long & needle like with ventral groove. The epipharynx is fused with the labrum forming labrum- epipharynx.
Function:-
It covers the labial groove dorsally from inside. This structure appears C – shaped in transverse section having a groove called food channel.


3. Hypopharynx:-
Food channel is closed below by a long, pointed & flattened plate, like a double edged sword, called hypopharynx. It possesses a salivary duct, opening at its tip.
Function:-
 Through this duct saliva is poured to prevent coagulation of  blood during sucking.


4. Mandibles & maxillae:-
Within the labial groove lies paired, long, needle shaped mandibles & maxillae. Mandibles end in sharp tiny blades, while maxillae into saw like blades bearing teeth.
Function:-
Mandibles & maxillae act as piercing organs.


In male the labrum-epipharynx & the labium are the same as in the female, but the mandibles & maxillae are very short & functionless & the hypopharynx is fused with the labium.


Mechanism of feeding:-
The normal food of both sexes are nectar of flower & juices of plants, but the female possesses modified mouth parts for obtaining additional meals of blood of vertebrates.
A female mosquito sits on a vertebrate & presses its labellae of proboscis against the skin. Labellae act as a guide for the piercing mandibles & maxillae.
The labium bends back and mandibles & maxillae pierce deep into the skin in order to puncture the blood capillaries.
 Saliva, acting as an anticoagulant, is injected down the hypopharynx into the wound.
The labrum-epipharynx & hypopharynx together form a feeding tube to suck up blood.
The suction is caused by the pharynx by which blood comes into the mouth.