When most people think of spiders and how they eat, they picture an orb shaped web with a housefly stuck fast, and a spider lurking in the middle ready to devour it. However there are actually a great range of different ways that spiders both hunt and eat their food.
A common misconception is that all spiders can only ingest completely liquefied food, although this is not strictly true. Although spiders generally have very narrow digestive tracts, they can in fact consume small pieces of solid food that have been sufficiently cut up.
The major difference in how spiders ingest food lies in what kind of fangs they have. Most spiders have fangs that point inwards towards each other, and many can use them to cut pieces of a prey item into smaller pieces. While most will use venom to liquefy their prey as well, they are known to eat smaller solid pieces if they are sufficiently small.
Species of spiders belonging to the infraorder Mygalomorphae though have fangs that point downwards, and as such cannot be used in this manner. Mygalomorphae species include tarantulas, funnel webs and trapdoor spiders. They tend to hunt using an ambush method and their fangs tend to be much bigger in relation to their body size. Because they have no means of tearing their prey into edible pieces, they instead have to wait until their venom liquefies the insides of the prey.
In addition there are several other groups of arachnids that can often tend to be confused with spiders although are in fact from a different order. Solifugae for example are commonly called sun spiders, and are also known by the notorious and somewhat misunderstood name of camel spiders. They in fact do not have fangs or venom, but jaws which they do use to tear their prey into pieces. however they are not true spiders and cannot produce silk.
Rather than the method of actually ingesting their prey though, the methods of hunting among spiders is where the real variety can be found. Of those that build webs, they generally tend to either paralyze or kill their prey with a bite after it has been caught. If the prey is either too large or presents a threat to the spider, for example something like a wasp that has a sting, they may leave it for some time to tire before they attempt to bite it.
The venom of most spiders will then liquefy the insides of the prey, although some also inject or vomit digestive enzymes either separately or instead. The spider then ingests this liquid, leaving behind the empty husk. If you look at either a spider web in an effective hunting area late in the day, or the ground below a web, you can often see the dried remains of insects scattered about that the spider has previously fed on and discarded. If the spider is not hungry but continues to catch prey, then they will often wrap their prey in silk cocoons for later use.
Within this group there are two further distinct groups, one which produces sticky webs and one which produces very fine webs. Sticky webs are most commonly seen outdoors, a prime example being the iconic orb shape with a center, several spokes radiating from it and connective strands of silk between them. Some species though have what appears to be a tangled mess rather than an organized shape to their webs, although they are similarly effective.
Dry or fine webs tend to look more like a white or gray sheet, and have very closely woven strands. They are more commonly found indoors, and will often be see in the corner of a room or between pieces of furniture. Differing from sticky webs, prey species tend to get tangled in between the strands of dry webs because of the fact that the strands are loose and will give way underfoot. These spiders will usually build a silken tunnel close by rather than sitting on the main web itself, and will rush out if prey comes too close. Their webs strands often in this way act as tripwires rather than actually disabling their prey.
Spiders who build sticky webs will tend to bite prey when it has sufficiently tired itself out from struggling. Spiders who produce dry webs however usually attack their prey immediately upon feeling the vibrations of an intruder through the silk strands of their web. This is mainly because given sufficient time an insect will be able to free themselves from this kind of web.
The other major group of spiders are broadly known as hunting spiders, in that they actively seek out their prey rather than waiting for it to come to them. Hunting spiders will generally be more robustly built than web dwelling species, and will also often have larger fangs with more potent venom. The reason being that they are more likely to face resistance from their prey, and they need to subdue it more quickly in order to avoid injury.
Hunting spiders come in many forms, but most will tend to ambush their prey from behind if they can, delivering a fatal or paralyzing bite before much resistance can be offered. Wolf and jumping spiders fall into this category so called because they tend to stalk and jump on their prey respectively. A common species of jumping spider is the Zebra spider which can often be seen darting vertically along walls in the summer time.
