Pithus is the closest analog the Ananasi have of the Hispo form of the Garou. It is, however, absolutely enormous compared to a regular spider, and a closer inspection would reveal that, aside from its size, this form has several other strange characteristics.
This form may at first glance look like a regular spider, just enormous, but also a bit more monstrous. But at closer examination, several of the organs, especially the heart and lungs, as well as the blood are actually a mixture of human and spider. If this was not the case, the Pithus would not be able to breathe, as real arthropod anatomy can't support something even close to this size. Even the digestive system and the sensory organs are actually more of a mixture of human and spider anatomy. Unlike what many think, most Ananasi in Pithus are fully capable of eating normal food, though most prefer liquid food, like blood and meat liquefied by their saliva and venom. Females are generally larger and more powerful in this form than males, who tend to be smaller and more nimble.
The species of spider the Ananasi belongs to gives the general look of the form, but not exactly. The eyes often look a bit strange, and there can be the wrong number of them, and the limbs tend to be proportionally thicker than that of a regular spider. For those with a Crawlerling form of mixed species, the Pithus form can either have something of an amalgam appearance, or for Arachnid born, being that of the species the Ananasi was born as.
It is in this form that the Ananasi can produce enormous webs, and have the most massive fangs and is capable of injecting the full dosage of venom (even if the species the Ananasi belongs to can't produce webs and venom, so it will always have spinnerets). The pedipalps (arms) may be small and quite ineffective in combat, but all legs will have the equivalent of claws, and especially the front legs are effective at both clawing and grappling, just like arms. The limbs are however not capable of grasping objects and doing fine manipulation to the degree human hands are, so it can't wield weapons. The form is however to massive to climb on flat walls and similar without the use of Gifts.
In Pithus, the Ananasi may only speak the special language of the Ananasi, and communicate as a "regular" enormous spider. The mouth parts are not similar enough to human to be able to communicate as a person.
This is the original form of the Ananasi, from long before humans, and it is their preferred form while preforming rites (they can however do so in any form), and is the breed form for the rare Ananasi Metis. Many prefer this form in formal situations with other Ananasi, and it is also a very good combat form. If the Ananasi should change species of spider, the appearance form will change too.
Among the Kumo, the Pithus form is known as "Aghora". In this form, the Kumo possesses a special supernatural tainted venom that even affects shapeshifters and other supernatural creatures. This special venom does not consume any of the venom dosages. In their other forms, their venom works just like their western cousins.