354 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



through it in digging up a plant. The moss on the trap grew as vigor- 



ousl}% and had in every way the same appearance, as that rooted in the 



surrounding earth, and so perfect was the deception that Mr. Mog- 



Mimetic gi-idge found it impossible to detect the position of the closed 



rap- door, even when holding it in his hand. No doubt many nests 



doors. ' .... -r- ■ ■ 



escape observation m this way, and the artmce is more surjaris- 



ing because there is strong reason to believe that this doer garden is delib- 

 erately planted with moss by the spider, and not the effect of mere chance 

 growth. 1 Figs. 4 and 5 represent a section of earth covered with a delicate 

 moss, which includes the trapdoor of Nemesia coementaria. The door is 

 shown open at Fig. 4 and closed at Fig. 5, and the concealment of the door, 

 although not so striking as in Fig. 3, is nevertheless quite manifest. 



In the case of Trapdoor spiders which make a thin or " wafer door," as 

 Moggridge calls it, there is but a thin coating of earth on their upper sur- 

 face, since it is rare to find any of the larger mosses or lichens growing 

 upon them. But, as if to compensate for this deficiency, a variety of for- 

 eign materials is employed, which are scarcely ever found in the thick cork 

 doors, such as dead leaves, bits of roots, straw, of grasses, etc., and Mog- 

 gridge had seen freshly cut green leaves, ajiiiarently gathered for the pur- 

 pose, spun into a door which had recently been constructed. ^ 



There is the widest possible difference between nest and nest in the de- 

 gree of perfection in concealment ; and although, as a rule, the surface of 

 the upper door harmonizes well with the general appearance of 

 ^ ^. " its surroundings, there are some individual nests in which it 

 readily catches the eye and even attracts attention. Mr. !Mog- 

 gridge saw nests in mossj'^ banks wliere the door, being made of nothing 

 but eartli and silk, showed distinctly as brown patches against the green. 

 These doors even when surrounded by earth were often easily detected, 

 because when they dried up, as they quickly did, they became much paler 

 in color than the earth of the bank which retained its moisture.^ 



Thus it seems that the simple instinct to cover in the door, and so 

 protect the artificer from exposure to weather and enemies, was the domi- 

 nant motive. IShiterial was chosen from the immediate vicinage suitable 

 and convenient for closure, and no purpose appears in the act to select 

 such material as would disguise the nest. In other words, a sense of se- 

 curity by means of sheltering barriers dominated the spider's mind, and 

 security by means of mimetic harmony or protective resemblance appears 

 to have had no place at all. 



Some support for this opinion appears to me to be derived from Mr. 

 Moggridge's statements as to the mode in which some of these Trapdoor 

 spiders work. He fastened back the doors of several tunnels, in order to 

 test the mode in which the inmate would deal with this difficulty. In one 



' Trapdoor Sjiiders, page 97. - Ibid., page 103. ^ Ibid., page 103. 



