Homonotus sanguinolentus preys on one species of spider, Cheiracanthium erraticum, which lives on the damper patches of heathlands.

From late June until August the female spider spins a purse-like web using vegetation such as heather inflorescences and grass flowering stems.

The H. sanguinolentus larva then spins its cocoon within the spider's purse-web.

The purse-web has to remain intact and above the ground until the following July when the new adult H. sanguinolentus emerge.

In the United Kingdom it is a Biodiversity Action Plan species.