Types Of Mouth Parts In Insects-I
Insects feed on animals and plants in a diversity of ways and their mouthparts have become modified for these purposes. The mouthparts are essentially the paired appendages of the mandibles and the maxillary and labial segments of the head. These have evolved into a variety of forms, which have been perfected to meet different kinds of highly specialized feeding habits. The important types of insect mouthparts can be described as follows.
The maxillary palps act as sensory to locate the food. The lacinia are often employed for grasping the food and cutting or chewing it. The mandibles, worked by two sets of muscles, masticate the food with their tooth-like processes. The ligula formed by the paired glossae and paraglossae, help in pushing the food into the pharynx.
The biting and chewing types of mouthparts are common among Orthopteran insects such as grasshoppers, cockroaches and crickets. They also occur in silverfish (Lepisma), earwigs, termites, book-lice, bird-lice, beetles, some Hymenoptera and many larval forms, specially the caterpillars of Lepidoptera.
In mosquito, the mouthparts consist of a long proboscis or beak, which is composed of the labium, forming an elongate, fleshy and mid-dorsally grooved tube. It encloses the needle-like stylets formed by the modifications of the mandibles, maxillae and hypopharynx. The needle-like labrum is fused with the epipharynx and forms the long covering of the open groove of proboscis. The proboscis bears at its tip, two small labellae, which used as feelers and enable the mosquito to select the appropriate part of its victim to attack. These mouthparts are well developed in female mosquitoes as they feed on blood.
In bedbug the labium forms a three jointed proboscis. The stylets are four in number, consisting of two mandibles and two maxillae, the former with blade-like and the later with saw-like tips. The labrum is a flap-like structure, covering the groove of proboscis at the base only. Of the four stylets the maxillae are doubly grooved on their inner faces, one acting as a food canal for the flow of blood and the other as a salivary canal for the flow of saliva.