BIOLOGY Volume 1 - A Guide to General Biology - 2004

8. HETEROTROPHIC NUTRITION

8.2. Animal Feeding Mechanisms

8.2.4. Biting and Chewing Mouthparts

Many insects feed on plant material, and their mouthparts are adapted for biting and chewing plants. Some herbivorous insects cause severe damage to agricultural crops. One of the most prominent Examples of such insects is the locust. Its mouthparts have a complex Structure (Fig. 8.7). To better understand the design of the insect's mouthparts, we will examine the overall STRUCTURE OF THE insect body in a little more detail. It consists of a series of segments (Section 2.8.6). Each segment bears a pair of jointed appendages. In the HEAD region, these appendages may be modified for feeding purposes. The locust uses the appendages of the 4th, 5th, and 6th segments of the head as its mouthparts. These appendages surround the Mouth, which is located on the underside of the head. Fig. 8.7 shows the sequential arrangement of the elements of the locust's mouthpart apparatus. These include the upper lip (labrum), a pair of upper jaws (mandibles), a pair of lower jaws (maxillae), and the lower lip (labium). The mandibles are located on the 4th segment, the maxillae on the 5th, and the lower lip (a fused pair of appendages) on the 6th.

Class="center">

Fig. 8.7. A. Locust mouthparts. B. Frontal view of the locust's head showing the mouthparts.

When feeding, the locust firmly grips a leaf between its upper and lower Lips. Moving from side to side, the mandibles bite off and shred pieces of leaves. Also aided by the maxillae, the lower lip, which contains saliva, pushes the moistened food into the mouth, where it is swallowed. Sensory appendages called palps allow the locust to identify food by its Smell and Taste.

Locusts are major pests in warm Regions of the world, including Africa, India, Pakistan, the Middle East, and South America. Locust plagues in ancient Egypt are described in the Bible. Locust outbreaks occur at irregular intervals and last for several seasons. The locust population gradually grows from a low density to a high density located in the "outbreak epicenter"; when food in the epicenter becomes limited, a large portion of the population begins to migrate to new habitats. At this stage, locusts gather in massive numbers, and all adults migrate simultaneously as a giant swarm that can comprise more than 10 billion individuals. These hordes are capable of consuming over 100,000 tonnes of food a day (Fig. 8.8). They can completely destroy large areas of vegetation, devastating agricultural land and leading to severe famine. International cooperation ensures ongoing monitoring of locust populations. Combined with research into locust migratory behavior, this enables a rapid response to minimize the damage caused. High-risk areas are identified in advance and sprayed with insecticides. Locust swarms are tracked and destroyed using aircraft and ground equipment.

Fig. 8.8. Swarming locusts.