Insects in general are a terrific nuisance when it comes to the home. There are so many different types and Species of Insect that can cause harm to both you and your home.
From garden insects to 
house-bound creepy crawlies, all cause there own unique problems and almost all have very different methods of treatment.
Garden Insects
Garden Insects are a specific annoyance to farmers and cultivators of plants, bushes and trees. As well as inhibiting growth and appearance of all manner of garden species, garden insects can eat through enormous quantities in a very short time.
For example, the Caterpillar is a very small garden insect, yet there are so many varieties and they are very common in all areas of the world.
The reason these garden insects are a pest is because they can eat through large quantities of plant matter, and if you have a bad infestation it is likely that they will destroy most of the garden as they are not always particularly fussy about which types of plants they eat.
Other common garden insects include Greenfly and Aphids, which also eat through plants but at a much slower rate. They can also cause plants to become diseased, and Plant Diseases can spread in the same way that human diseases can.
These common garden insects can be treated with Pesticides and specially formulated plant sprays, but a lot of people do not like to use them as they can inhibit flavour and cause potential problems in humans if digested. The only aid that humans get is from Ladybirds, who like to eat aphids.
Insects in the Home
The most predominant indoor pest is the common Housefly. The method in which this species devour their food is by regurgitating 
on whatever it is they are eating. This 'vomit' actually breaks down the food into a sloppy liquid that the fly can then suck back up.
They have no teeth or pincers, so are unable to chew anything so this method is the only way for them to consume their food.
The most disgusting point when referring to flies is that they like to eat some of the most disgusting things you can imagine, such as dog excretion and carrion.
It is, unfortunately, not uncommon that a fly will have eaten some form of excretion, or carrion just before they land on your food with the same feet and begin the same process of vomiting and sucking the food back up. Always make sure food is covered, and that waste food and other smelly items are covered and put away.
It is also worth noting that a lot of insects that you may see roaming around your house, even down to the minute Carpet Beetles that make their homes in rugs and carpets, can carry some form of illness or disease which can be potentially harmful to humans. Always keep your house clean and tidy to prevent anything causing harm to you or your family.