A fully executed contract date begins once both parties signed it. In your case, since you signed them first, the date begins when the seller/affixes his signature. However, the delivery of the ratified contract should also be considered. Consult your realtor and a lawyer.
A group of spiders is called a cluster or clutter. Spiders belong to the group of animals called arachnids.
Scorpions are in the Order Scorpiones, spiders are in the Order Araneae, ticks and mites are in the Order Acari. The creatures most correctly called daddy-longlegs are in their own separate Order which is Opiliones. Common names for this Order are 1) daddy-longlegs, 2) harvestmen and 3) opilionids.