"Howdy! That's a great question, actually. The reason we fart is due to needing to periodically release gases that build up during digestion. During the digestion process of the foods you eat, naturally occurring beneficial bacteria in your body metabolize (i.e. convert the food in your body to useable energy) and produce waste as a result, some of which is the gas that makes up farts. This is typically where the methane (CH4) in farts comes from, the rest of the fart volume being from air swallowed during the course of the day. For animals like spiders and insects, there are similar processes! Some animals like termites, for example, better match us as they, too, have methane-producing bacteria in their guts which helps them break down wood! For other animals, other digestive processes make waste products and sometimes gas, so yes, spiders (and insects) do fart, in a sense! Since their exoskeletons are generally rigid, though, they may not produce the sound we associate with farting, thus, you might say that most spider and insect farts are "silent but deadly"!"