eee eS 
OF AP Tk. oe ci 
ENGINEERING SKILL OF SPIDERS. 
It 
Iv is a generally received opinion, even among well informed natural- 
ists, and is certainly a fixed popular tradition, that Orbweaving spiders 
construct a web that is perfectly true in its geometric arrange- 
Imperfect ment. This has highly redounded to the praise of the little 
Geomet- weayer, particularly as she may spin by the sense of touch with- 
ric Ar- 5 : 1 : : . 
anges out the aid of sight.' It seems a pity to destroy any notion 
mann that may throw around despised Arachne a greater measure of 
respect in the popular mind, in which her standing is, as a rule, 
anything but favorable. However, in the interests of truth it must be said 
that concerning this point the popular opinion is .only true in a general 
sense. There is much irregularity in the execution of many geometric 
webs. 
The radii are not laid out with absolute mathematical accuracy, but 
are separated from each other by distances varying considerably. If, for 
example, one carries the eye around the circumference of this large orb, 
he will find here two radii terminating upon their marginal foundation 
lines at points half an inch apart, and there two others three-fourths of 
an inch apart, and in yet another place two others separated by one and 
a half inches. It is true that all orbs are not laid out as irregularly as 
this from whose measurements I have quoted, but more or less irregularity 
will be found on almost every web, particularly upon those spun by adult 
spiders. Again, the radii will be found blending with one another at 
various points instead of converging regularly upon a central point ; and 
more or less departures of a like kind from mathematical accuracy char- 
acterize the spiral concentrics. However that may be, the actual facts in 
the case are sufficiently striking, and the general regularity of plan and 
the frequent close approach to geometric accuracy in special orbs 
Symme- are remarkable enough without resorting to exaggerations. In 
i fea fact, it may well be doubted that absolute regularity, in the 
sense of symmetry, would be the most desirable for the uses of 
a web. The departures from mathematical accuracy may mark, and I 
haye reason. be believe do mark, a higher measure of utility, and 
1 See Wood's of ‘emied without Hania! page 321. 
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