Food Digested Externally

macro close up of a common house fly with a brown and black body with large red eyes and white background

Biological Strategy

House fly

AskNature Team

Image: Tobias Roth / Unsplash / Free non-commercial use

Chemically Break Down Organic Compounds

The vast majority of biochemical assembly and breakdown processes–even by the most complex organisms–occur within cells. In fact, cells are able to perform hundreds, even thousands of chemical transformations at the same time under life-friendly conditions (ambient temperature and pressure in an aqueous environment). Part of the reason that decomposition reactions (chemical breakdown) can occur under such mild conditions is because most often, they occur in a stepwise, enzyme-mediated fashion, sipping or releasing small amounts of energy at each step. For example, the breakdown of glucose to pyruvate–and the release of energy–occurs in the 10-step enzyme catalyzed process of glycolysis.

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Insects

Class Insecta (“an insect”): Flies, ants, beetles, cockroaches, fleas, dragonflies

Insects are the most abundant arthropods—they make up 90% of the animals in the phylum. They’re found everywhere on earth except the deep ocean, and scientists estimate there are millions of insects not yet described. Most live on land, but many live in freshwater or saltwater marshes for part of their life cycles. Insects have three distinct body sections: a head, which has specialized mouthparts, a thorax, which has jointed legs, and an abdomen. They have well-developed nervous and sensory systems, and are the only invertebrate that can fly, thanks to their lightweight exoskeletons and small size.

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Houseflies digest their food externally by apply a solvent liquid to food particles to dissolve them, and then suck up the liquid food.

“The housefly uses the labellum in its mouthpart to ‘quality test’ food before feeding. Unlike many creatures, flies digest their food externally. It applies a solvent fluid to the food. This fluid dissolves the food into a liquid that the fly can suck. Then, the fly takes the liquid nutrients into itself by means of the labella which gently dabs liquids into its proboscis.” (Harun 2002:38)