2 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
Vi 
The trapdoor building habit is remarkable in its distribution over nearly 
every part of the globe in tropical and semitropical regions. From what- 
ever part reported, Europe, Africa, Asia, Australia, or North and 
Architec- South America, the nest shows the same peculiarities of structure, 
bi and the architect appears to live in the same way. Even the habit 
imicry. ele : : 
of mimicking the surrounding surface by attaching sundry small 
plants is cosmopolitan. Moggridge in his charming book has already made 
us familiar with this form of mimicry in the European species; it seems 
also to characterize our southwestern trapdoors, and appears in Cambridge’s 
Idiops Colletti, a Burmese (India) spider.1_ In the interesting description of 
General Collett, which Mr. Cambridge publishes, it is stated that the upper 
surface of the door is often covered with a dry black lichen growth. 
There are generally a few withered grass blades worked into the edge of 
the door, or into the edge of the mouth of the burrow, so as to form a 
kind of semicircular fringe, which often catches a practiced eye and 
leads to the detection of the hole. The grass blades are probably inserted 
to aid in assimilating the outside of the door to its surroundings, a pur- 
pose in which, General Collett opined, they certainly fail so far as the 
human animal is concerned. In a few cases he noticed also grass blades 
wrought into the general surface of the door, which in the dry 
A Rude season, when the grass is everywhere withered, certainly aid in 
Door ; : ; ; 
Garden, 18 concealment. But during the season when the adjacent grass 
is green one would think that yellow withered grass blades on or 
near the burrow mouth would tend to make it conspicuous. I haye con- 
sidered at some length, Vol. II., pages 354, 355, the point thus raised in- 
dependently by this intelligent observer, and its relation to so called 
mimicry of environment. I need only add here that one can hardly be 
asked to consider protection against human intelligence as a factor in the 
action of a spider’s mind. The hostile elements which influence it are of 
quite another sort from the curiosity of a naturalist and the plundering of 
a collector, 
VI. 
Since publishing my observations on the parasitic enemies of spiders 
(Vol. IL, page 391) a number of facts have come to my hands which I 
have thought well to embrace in these studies, and to add some 
general conclusions suggested by the subject. Mr. George Carter 
Bignell? has favored me with an account of the manner in which 
Drassus lapidocolens Walckenaer was attacked by an ichneumon (8th Oc- 
tober (1890). While walking in the woods he noticed the spider suspended 
by a silken drop thread from the bough of a large as Looking for the 
Parasit- 
ism. 
‘Proceed, Zool. Soe., Tena 1889, page 37, pl. ii., Fig. 2. 
*7 Clarence Place, Stonehouse, Devon, England. 
