It took the shaking of the web to decide them to attack.
Perhaps the grey colour of the Locust is not sufficiently conspicuous to attract attention by itself.

Then let us try red, the brightest colour to our retina and probably also to the Spiders'.

None of the game hunted by the Epeirae being clad in scarlet, I make a small bundle out of red wool, a bait of the size of a Locust.

I glue it to the web.
My stratagem succeeds.

As long as the parcel is stationary, the Spider is not roused; but, the moment it trembles, stirred by my straw, she runs up eagerly.
There are silly ones who just touch the thing with their legs and, without further enquiries, swathe it in silk after the manner of the usual game.