Phillips. — On Spiders as Engineers. 601 



the evening before or during early morning, each web being 

 loaded with the fine particles of fog or dew. There had been 

 very heavy rain on the 7th, so that the webs must have been 

 spun out during the previous six or twelve hours from the time 

 I noticed them — 7.30 a.m. on the 8th. (It has never been pro- 

 perly explained by Darwin that by any process of reasoning a 

 spider knew that it was safe to throw out its web, and that 

 the day was going to be fine. I propose hereafter to read to 

 members a paper bearing directly upon this subject, and being 

 a continuation of the paper I had the honour of reading before 

 members upon the Common Vital Force.)* 



The first thing that really struck my eye was the heavy 

 shore-stay construction of one of these bridges, and I got down 

 to examine it. It was a typical suspension bridge, quite taut, 

 but the shore- stays much more extensive, heavy, and intricate 

 than our engineers usually make. It had two long down- 

 stream steadying stays fastened to each bank ; height above 

 water, about 2ft. Drain itself, 4ft. to 5ft. wide, running through 

 a fallen and burnt 5-chain track in the bush. The next bridge 

 was a double bridge joined together by a centre span, but with- 

 out so many shore-stays. The next one was also a double 

 bridge, with strong upstream stays. The different parts of 

 these double bridges appeared to support each other consider- 

 ably. 



The tautness of many of the bridges was peculiar, spiders' 

 bridges being usually limber and free. Some of the double 

 bridges were evidently accidental ; but there could be no mis- 

 take in the tautening-up. No matter how the web crossed 

 the stream, or crossed another web, the tautening-up when 

 necessary put everything straight, and the structure itself in 

 tension. The animal knew, I suppose, that in crossing water 

 it would be necessary not to have too much play in the web, in 

 order to avoid taking a plunge at times in the water itself, or 

 the water rising to catch the slack. 



No radiated-sail prey-web was hung upon any of these 

 bridges. These were all suspended immediately on the side 

 of the drain, or slightly overhanging the water, or upon the 

 fallen burnt bush. There were vast numbers of these geometric 

 webs, and very pretty they looked. I never remember seeing 

 such a vast quantity, all of which must have been thrown out 

 within the previous few hours. The animals perhaps were 

 starving after a two to three days' rain. As the webs were 

 spread out to the height of 8ft. from the ground upon any 

 burnt limb, and as there were as many as ten or a dozen webs 

 upon each limb, I thought at the time that it would be very 

 difficult for any flying insect to escape being caught in one of 



See Trans. N.Z. Inst., vol. xix., pp. 592 and 593. 



