How Insects Feed
Have you ever wondered about insects and how they feed? An incredible number of insects live on the planet, it is estimated that there are about 200 million insects for every human on earth. That gives us a lot of insects, feeding in four main ways. Microscopic examination of the insect world will show us how they feed. Scientists will use this information to tackle insect pests which damage crops, feed on animals (including humans) and spread disease.
Examples of chewing insects are beetles, grasshoppers and dragonflies. Some insects also chew food in their larval stage, such as caterpillars, which then turn into butterflies and moths.
If we examine these insects we will see some specialised mouth parts, mandibles, maxillae and labium (fused maxillae) which the insect will use to tear and rip at the food stuff. Viewed with an optical microscope there mouth parts look like woodworking tools such as saws and pincers. Some insects can decimate food crops, destroying all the softer parts of the plant and killing it.
Some insects, such as butterflies and moths, use an adapted mouth part, the proboscis, as if it is a drinking straw, to sip food in liquid form, such as nectar, from a food source. When not in use it can be coiled away, in some insects it can be significantly longer than the whole insect. If larger insects are viewed the proboscis can be clearly seen, especially when the insect is feeding, but the true beauty of the structure is best revealed with a microscope.
In some moths the proboscis is adapted so that they can pierce fruits to feed on the juicy inner flesh. These moths can become a significant orchard pest, damaging fruit and spreading diseases as they feed.
In some insects such as mosquitoes and aphids, the mouth parts are adapted to be much harder, it is called a stylet and can be used to pierce flesh and access the food within the body of a plant or animal. Aphids can colonise food plants and attack them so vigorously that the plant is no longer able to grow and the affected areas will eventually die. This can impact the growth of food crops.
Mosquitoes spread diseases, typically malaria, but other diseases can be spread in the same way, from host animals and can cause significant ill health. Similarly the mouth parts of tick animals can be seen to pierce the skin and fix firmly into the flesh of the host animal until a ‘blood meal’ is taken. This might take anything up to a couple of days. Ticks can cause significant spread of disease, with Lyme Disease being of most concern. Looking at the mouth parts of a tick under a microscope shows a structure which bores into the flesh and is difficult to remove, and can leave the head and mouth parts embedded in the flesh, leading to a nasty wound.
The most commonly know of the sponging insects is the housefly, where the mouth parts are specialised to form a thicker sponge like structure. Through this the housefly secretes saliva and is then able to draw the saliva plus partially digested food into the body. This is the reason why food should be protected from house fly ‘browsing’ as there is a significant risk of the spread of disease from the feeding process.
Using a microscope to explore the fantastic range of variations within the insect kingdom helps us to understand how to manage and control these animals when their feeding represents a challenge to food production or health.