480 Handbook of N ature-Study 



another. It may make its first radius by dropping from its bridge to 

 some point below; then climbing back to the center, it fastens the line for 

 another radius, and spinning as it goes, walks down and out to some other 

 point, holding the thread clear and then pulhng it tight before fastening it. 

 Having thus selected the center of the web, it goes back and forth to and 

 from it, spinning lines until all of the radii are completed and fastened at 

 one center. It then starts at the center and spins a spiral, laying it onto 

 the radii to hold them firm. However, the lines of this spiral are farther 

 apart and much more irregular than the final spiral. Thus far, all of the 

 threads the spider has spun are inelastic and not sticky; and this first, or 

 temporary spiral is used by the spider to walk upon when spinning the 

 final spiral. It begins the latter at the outer edge instead of at the center, 

 and works toward the middle. As the second spiral progresses, the spider 

 with its jaws cuts away the spiral which it first made, and which it has used 

 as a scafl^olding. A careful observer may often see remnants of this first 

 spiral on the radii between the lines of the permanent spiral. The spider 

 works very rapidly and will complete a web in a very short time. The 

 final spiral is made of the elastic and adhesive silk. 



References — Comstock's Manual; Common Spiders, Emerton; The 

 Spider Book, Comstock; Nature's Craftsmen, McCook. 



LESSON CXII 

 The Orb-web 

 Leading thought — No structure made by a creature lower than man is 

 so exriuisitely perfect as the orb-web of the spider. 



Method — There should be an orb-web where the pupils can observe it, 

 preferably with the spider in attendance. 



Observations — i. Is the orb-web usually hung horizontally or ver- 

 tically? 



2. Observe the radii, or "spokes," of the web. How many are there? 

 How are they fastened to surrounding objects? Is each spoke fastened 

 to some object or to a framework of silken lines? 



3. Observe the silken thread laid around the spokes. Is it a spiral 

 line or is each circle complete? Are the lines the same distance apart on 

 the outer part of the web as at the center? How many of the circling 

 lines are there ? 



4. Is the center of the web merely an irregular net, or are there bands 

 of silk put on in zigzag shape? 



5. Touch any of the "spokes" lightly with the point of a pencil. 

 Does it adhere to the pencil and stretch out as you pull the pencil away? 

 Touch one of the circling lines with a pencil point, and see if it adheres to 

 the point and is elastic. What is the reason for this dift'erence in the 

 stickiness and elasticity of the difl"erent kinds of silk in the orb-web? 



6. If an insect touches the web, how does it become more entangled 

 by seeking to get away? 



7. Where does the spider stay, at the center of the web or in a little 

 retreat at one side? 



8. If an insect becomes entangled in the web, how does the spider 

 discover the fact and act ? 



9. If the spider sits at the middle of the orb, it has a different method 

 for discovering when an insert strikes the web than does the spider that 

 hides in a den at one side. Describe the methods of each. 



