But what keeps the tiny spiders alive? Magic...or the sword might release an insect attracting smell (around midnight to avoid swarming the user with potential bloodsuckers/pests) and the insects are trapped in the web construct and drained dry in minutes, then discarded. Such ability would keep the tiny helpers fed, as well as keep insects away from the owner at nights, provided it leaves the sword a little away from themselves...risky but also a bit safe at least from insect night-attacks. The other means of feeding is done by the blood of those the weapon strikes. The blade is cleaned of any blood or other type of body fluids by the same little helpers.