174 PROCEEDINGS OF THE ACADEMY OF [1888. 



the central depression. Dr. McCook added that, as far as he knew^ 

 no araneologist had suggested the tlieory of niusicular attachment 

 and action as effecting color distribution, and he did not -svish his 

 opinion for the present to be considered as fixed ; but he thought 

 the theory probable, at least. 



II. On the Relation of Environment and Habit to Color Changes, 

 it was observed : 



1 Spiders that live upon plants as a rule have colors that are 

 harmonious with the prevailing greens and yellows, and admixtures 

 thereof, of branches, leaves and flowers. 



2 Spiders that nest in stables, houses, on fences etc., ordinarily 

 have dusky colors, harmonious with the environment. Examples, 

 Theridion vidgare, Agalena ncevia, Tegenaria medieinalis {Durhamiy 

 etc. However, the speaker di<l not find that any great difference in 

 color is observable in the above species when they are found nesting 

 in foliage, as is often the case, at least with Agalena and Theridion. 

 It might be said, perhaps, that there is a slight tendency to darker 

 and a more uniform color when the spiders are found in the first 

 named locations. 



3 Ground spiders (the Lycosids etc.) generally have colors of 

 neutral grays that blend well either with the soil, with rocks or with 

 stalks of grass etc., especially Avheu the latter are somewhat dry.* 

 Lycosids found in the neighborhood of streams do not seem to be es- 

 pecially influenced by the natural color of water ; but Dolomedes 

 sexpunctatus, which is so constantly found on the water, frequently 

 has a tint like that of the stream itself. 



4 Saltigrades follow the rule of the Lycosids as to color. Their 

 colors harmonize well with the surface of rocks, trunks of trees etc., 

 upon which they habitually seek their prey. They are also sufl&- 

 ciently harmonized with the color of leaves and the ground. 



The metallic green on the fangs of some Saltigrades seems almost 

 like a green leaf-ambush to the body of the creature as it is observed 

 stalking its prey. This suggests the strategy most familiar from its 

 association with the lines of Shakespeare : 



" Macbeth shall never vanquished be, until 

 Great BirnamAvood to the Dunsinane hill 

 Shall come against him." 

 Of course this suggestion is fanciful ; but of what use to the crea- 

 ture can such a provision be if it serves not as an aid in securing 

 its prey or protecting it against enemies? One might almost be jus- 

 tified for asking : can there possibly be anything in the above idea? 



5 Are the brightest colored spiders, which one would suppose 

 naturally to be most exposed to enemies like birds, and raiding ich- 

 neumon-flies and mud-dauber wasps, commonly protected by their 

 industry? Dr. McCook cited a few examples as bearing upon this 



* It is a fact that the darker colors of most spiders are found contemporaneously 

 with the autumn changes of the foliage to a duskier hue, but the two facts are 

 probably due to the same cause, viz., the advancement of decay and the changes 

 ■which result from this last named stage of vitality. 



