944 The American Naturalist. [October, 
ficially induced by heating uric acid with water in sealed tubes at high 
temperatures, and the identity of the natural and artificial products 
may be demonstrated by the similarity of their spectrum. Mr. Hop- 
kins believes that this yellow substance, which may be called lepidotic 
acid, together with a closely allied red substance, will account for all 
the chemical pigmentation of the wing scales of the colored Pieride, 
though modifications may be produced by superadded optical effects. 
These uric acid derivatives, though universal on the Pieridæ, are ap- 
parently confined to this group among the Rhopalocera. This fact 
leads to the interesting observation that where a Pierid mimics an in- 
sect belonging to anothers family, the pigments in the two cases are 
chemically quite distinct. The fact that the scale pigments are really 
the normal excretory products of the animal utilized in ornament is 
emphasized by the observation that the yellow Pierids on emergence 
from the chrysalis are apt to void from the rectum a quantity of uric 
acid, colored by a yellow substance, which exactly resembles the pig- 
ment of the wing.—Journal Royal Microscopical Society. 
Sense of Sight in Spiders.—Professor and Mrs. Peckham in 
continuing their studies of spiders have published? some extremely 
interesting observations upon the sense of sight. Concerning the range 
of vision the authors think their experiments “ prove conclusively that 
Attide see their prey (which consists of small insects) when it is motion- 
less, up to a distance of five inches; that they see insects in motion at 
much greater distances ; and that they see each other distinctly up to 
at least twelve inches. The observations on blinded spiders and the 
numerous instances in which spiders which were close together, and 
yet out of sight of each other, showed that they were unconscious of 
each other’s presence render any other explanation of their action un- 
satisfactory. Sight guides them, not smell.” 
he authors also experimented with the color sense of spiders, and 
reached the opinion “ that all the experiments taken together strongly 
indicate that spiders have the power of distinguishing colors.” 
* Trans. Wisconsin Acad. X, pp. 231-261. 
