|MadSci Network: General Biology|
Hi. What a great question. It's nice to hear from people who think deeply about our six-legged friends. As a simple answer, yes, insects do drink in the same way as other animals, but there is a little more to it than that. Firstly, it depends on the rest of the insect's diet as you rightly point out. Many herbivorous insects get the majority, if not all, of their fluid from the food they eat because vegetation has such a high water content. I have some tropical stick insects and they certainly get all their water from the leaves they eat, although they are kept in a damp environment. It is also worth noting that their mouthparts are not particularly effective for drawing water anyway. It is not uncommon for insects to drink from the morning dew, from raindrops, or from the surfaces or edges of ponds. Leave a damp tissue out on a hot day (make it bright yellow to attract the most insects) and watch them come in to drink. If you watch with a magnifying glass you will see that they have many different ways of doing it; flies suck it up, and wasps use a tiny structure that looks much like a tongue. While mentioning wasps, it is worth thinking about nest building which is done by biting tiny pieces of wood and bark and chewing them into a paste from which the nest is made. This requires water and so the wasp needs to take on moisture for this purpose too. I have two giant millipedes (not insects, but arthropods all the same) that augment their cucumber and tomato diet with a considerable amount of water that they draw from the damp soil around them. As a general rule, the ability to go without water is confined to small animals, and the larger an animal is, the more it depends on water. This could suggest why the bigger insects are usually to be found in warm wet places such as the rainforests. Finally, to answer your question about carnivorous insects, lets look at robber flies and mantids. Both are ambush style predators, one of which is common worldwide, whereas the other is usually only found in warmer climates. Both have a diet that is made up of prey, but the robber fly will take juice from fruit and the mantis will sip water from leaves when it gets thirsty. The next time you're drinking lemon soda on a hot day, spill a little and watch what the wasps do. Obey your thirst - or whatever the advert says. Cheers, Justin.
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