42 F. 31. CAMPBELL — OBSERVATIONS OX SPIDERS. 



they are more dependent upon touch. Many species are more active 

 by night than by day, and the most intricate and symmetrical 

 snares can be made in the dark. "Whatever deduction we may 

 make from this must, however, be subject to the consideration that 

 our visual range lies between a minimum and maximum number of 

 vibrations in a second, which exclude the less recurrent waves of 

 radiant heat. These latter, for anything we know, may cause a 

 luminous sensation in other creatures, in the same manner as 

 sound-vibrations outside our auditory range produce on them an 

 appreciable effect. 



That spiders are capable of a delicate judgment of distance is 

 evidenced by the Salticus scenicm (a small common species, readily 

 recognised by its zebra markings), which springs some little space 

 to seize its prey. The same spider will often turn round as it is 

 running down the perpendicular side of a wall, and look upwards, 

 if a little sand be dropped so as to fall about six inches from it. 



From the nature of the external integument, the eyes of spiders 

 would seem to be fixed in one direction, yet microscopic examina- 

 tion of them when alive leads me to think that the spiders not only 

 have an adjusting power over the lenses, but that they also can 

 move the eye itself within the cavity covered by the transparent 

 cuticle. This is the only way in which I can account for the 

 frequent changes of colour, as well as of the form and position of 

 the colour, which take place in their eyes, and which resembles 

 that of a moving liquid globule. 



Spiders are generally not dainty in their food, but they have 

 their strong aversions. They will reject the caterpillars of the 

 currant moth {Abraxas Grossulariata) and of the "V" moth {Halia 

 tvavaria), while they generally discard the Ichneumonidte, if I may 

 judge of experiments made on Tegenaria domestica in confinement. 

 Mr. Moggridge* relates how he guided a beetle ( Chrynomela Banksii) 

 to the nest of a trap-door spider, how it was seized and forcibly 

 rejected, and how immediately afterwards a wood-louse was re- 

 tained. 



Habits. 



The eggs of spiders are enveloped in a cocoon, and the young 

 remain together a few days after they are hatched, when, if pre- 

 vented from separating, they attack one another. A common 

 practice employed by these young spiders to avoid their hungry 

 relatives, and one which does not seem at this early age to be 

 peculiar to any one species, is to stand rather higher than usual 

 and raise the end of the abdomen, like an angry bee, while the 

 viscid fluid before referred to is allowed to flow through the spin- 

 nerets, and form on their surface a loose entanglement of silk. In 

 this position they will remain until a current of air (even a gentle 

 human expiration is sufficient) draws away this rough parachute, 

 and with it a thread in communication with the spider. The 



* ( 



Trap-door Spiders,' Supplement, p. 40. 



