I know most spider bites are not dangerous, but can all spiders deliver some sort of bite/venom even if it won’t do any lasting damage?
Daddy Long Legs, despite being horribly poisonous, cannot bite humans.
I think this is an urban legend, but I was under the impression that they can’t bite because they have tiny mouths, which disqualifies them from the OP.
In fact, the animal I’m familiar with as a (grand) daddy long legs is not even a spider at all.
(Though I am aware there is an actual spider known as a daddy long legs).
The “most venomous” myth has apparently been applied to both, and is false in both cases.
Plus, the spiders we call daddy longlegs (harvestmen) are not even venomous.
All spiders are carnivores by nature, and I’d have to say that, yes, if its fangs are capable of penetrating human skin, they’re capable of biting humans and may do so if provoked. Of course, some spiders are meeker than others, but the capacity to bite is there.
As pointed out above, though, many spiders have fangs that are either too small or too fragile to penetrate thick, tough human skin. And a bite is not a guarantee that venom will be delivered, and the fact that venom is delivered does not necessarily mean that it’ll affect you in any negative way.
You might get super powers, though, so go ahead, start poking that spider!
Both harvestmen (arachnids but not spiders because they have only a single body part) and spiders of the Pholcidae family are called Daddy-long-legs. The claim they cannot pierce skin but are higly venemous is an urban myth. But the amount of venom they would deliver is too small to be of danger. There are nearly 800 species of Daddy-long-legs world wide, so a generalisation on their venom would not be valid. The effect of venom of different species, even when they are the same family, or even genus, varies.
The power of venom on humans is complex - we are not the target prey and so not of consequence in the evolution of the venom. For example, the venom of the Sydney funnel-web kills people, while it is harmless to dogs. The venom of one of the tarantulas now being sold here as pets is not fatal for people, but kills dogs and cats. Neither dogs nor people are the prey of spiders.
All spiders have venom to kill prey except those of the family Uloboridae - triangular backed orb weavers - about 240 species world wide (and two tiny obscure spiders of another family). They are often called humped spiders or hackled orbweavers, and can be identified because their orb webs are usually almost horizontal.
The size of the spider doesn’t give any clue to the power of the venom, but it is logical that larger spiders can pierce the skin of people easier than smaller ones. That doesn’t mean they will, though. The very large golden orb weavers are also very docile and there are very few records of them ever biting, despite being very common. Even when handled, they don’t react. The much smaller Lampona genus (our much maligned white-tailed spider) is more likely to bite. They are very common and bite readily, because they hide in clothes and bedding. There is another urban myth that they cause necrotic wounds, which has now been debunked.
I would be intersted to know what are the most common biters in other countries.
There is also the direction of the fangs. The trapdoor spiders, tarantulas, and the Australasian funnel-webs are known as ‘primitive’ spiders. They have powerful fangs which strike downward - hence they will raise their bodies to strike. Even if the venom is not fatal, the bite will hurt. The modern spiders have fangs which cross horizontally, and so they don’t raise their bodies to strike. Some do rear up to look aggressive.
So techncially the answer to the OP, I believe, is that all spiders are capable of biting and all except the Uloborids can deliver venom, but that doesn’t mean they will. Bigger means they can, technically, bite harder, deeper and deliver more venom. Their target prey are bigger, so that all makes sense.
Lynne