158 AMERICAN SPIDERS 



nary workmanship. Such diverse structures did not come into being 

 at a single stroke; they are the results of long, random experimenta- 

 tion, during which only those suited to the minimum needs of the 

 moment had survival value. From the first wild dragline threads laid 

 down in haphazard fashion on and around the egg sac have evolved 

 by progressive steps the many remarkable snares that today meet 

 the eye. At first there were mere tangles of lines stretched without 

 particular design, roughly filling an allotment of space between 

 suitable supports. Probably altogether composed of dry silk, these 

 mazes were suitable for stopping jumping or flying insects, and 

 retarding their movements through the entangling toils. The addi- 

 tion of viscous drops to the lines was a later development, which 

 transformed the stopping web into an adhesive trap. Among the 

 lines was stationed the egg sac the central theme, and the theoreti- 

 cal point from which all space webs take their origin. 



The first spiders that climbed into shrubs were daring adven- 

 turers leaving behind the soil domain so long cherished by their 

 forebears. They could become full-fledged aerial types only after 

 the web novelty had proved its worth as a means of providing food. 

 But once the space web was in reality successful, the incessantly 

 spinning spiders began to explore its possibilities in all directions. 

 Some suspended a horizontal platform of rather loosely woven silk 

 through the middle of the maze and maintained the egg sac at its 

 core. Clinging to the underside of this, they learned to seize insects 

 that, arrested in flight by the maze of threads, would drop to the 

 upper surface of the sheet. 



The orb web would seem to stand alone as a glorious creation, 

 an incredible novelty designed by superior artisans. That it is only 

 an advanced stage arrived at by the same slow steps that realized 

 the dragline, the stopping maze, and the horizontal platforms is 

 shown in the numerous intermediate examples. The orb web is 

 merely a formal expression of the horizontal platform. Probably 

 at first composed wholly of dry silk, it is now provided with a large 

 area of sticky spirals, and has been swung to a near-vertical position 

 to make it a more effective snare. Almost invariably associated with 

 it are some of the lines that were once the stopping maze. 



The space webs exhibit a most interesting evolutionary series. 

 Each major web type has been sponsored by different groups of 

 aerial spiders. The primitive line weavers still rely largely on the 

 tangle of threads for protection and as a means of stopping their 

 prey. The comb-footed spiders spin a maze, sometimes a sheet, and 



