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Why Sucking Mouths?

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All members in Hemiptera feed on a liquid diet. They suck food up the food canal. They feed on the fluids of plants, other insects and small animals, and the blood of larger animals. In all Hemiptera, the mouthparts arise from the front of the head, and the labium folds out of the way during feeding. Their piercing-sucking mouthpart is evolved from chewing mouth. The mandibles and maxillae are modified to form a food canal. The labium is also modified to form a grooved channel.

The major different of Hemiptera to other insects is their piercing-sucking mouthparts. Their sucking mouths are so success that their offspring become the new order in insects.

True bugs and Cicadas feed on plant by inserting their mouths into the plant and suck up juices. By doing this, there are some advantages. Since the bugs do not chew up the plants like grasshoppers, beetles and caterpillars, they take the food from plants on what they need. They make less waste, less dropping and hence less damage to the plants. This end up better for both the bugs and the plants. We can see that even there is many cicadas on a tree but they do little damages, if any, to the tree. 

However, in the later stages of piercing-sucking mouthparts evolution, some bugs life style evolved to the parasitic form to the plants, such as the Scale Insects. The insertion of mouthparts into the plants was used by the virus and bugs bring infections to the plants. Some bugs become the worst pest to the vegetations. This is another issue in the evolution.

Less waste also mean simpler digesting system. This could be the reason why bugs are usually smaller in size than beetles and grasshoppers.  Later some bugs insert their mouths into the body of other insects and become feeding on insects, where they go a detour path in evolution.  

Notice that there are other forms of sucking mouths in the insect class, such as the mouths of moths/butterflies and flies/mosquitoes.. Those insects’ sucking mouths are different and it is believed that those form of mouths are evolved more than once in insects evolution. This also indicated that chewing mouths may not be the most efficiency mouth for insects.

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Last updated: November 06, 2006.