In this neighborhood (Custer Co., Colorado,) one very frequently finds a yellow spider of the genus Thomisus or allied thereto, seated in the middle of the umbels Ligusticum montanum Benth and Hook., and on other yellow flowers. This spider, so seated, has nothing to cover it from direct observation, and from its size and colour would be conspicuous enough elsewhere; but on the yellow flowe, sitting in the depression in the centre of the umbel, it is quite invisible unless specially looked for.