The Zoologist— July, 1868. 1301 



a. Abdominal incisures luteous. .... 7. Populi. 



aa. Abdominal incisures of the ground hue. Abdomen bordered with 



green and brown at the tip. . . . .8. Salicti. 



Genus 12. Pterocallis, Passer ini. 

 Antennae with the seventh joint shorter than the sixth. In other 

 characters like Myzocallis. 



Typical species, Aphis Alni, Fabr. 



A. Abdomen with black marginal points. Veins of the fore wings with 



triangular brown spots at the tips. . . . . 1. Tilice. 



AA. Abdomen without marginal points. Veins of the fore wings not or 



hardly dilated at the tips. . . . . .2. Alni. 



Genus 13. Teama, Heyden. 

 Antennae with seven joints ; third joint longest ; seventh extremely 

 small. Legs long; hind tarsi with one joint. Winged form un- 

 known. 



1. Troglodytes. 



Genus 14. Paracletus, Heyden. 



Antennae short ; third, fourth and fifth joints nearly equal in length ; 



seventh very small. Abdomen depressed ; no nectaries. Legs long ; 



tarsi two-jointed. Winged form unknown. 



1. cimiciformis. 

 (To be continued.) 



How Spiders begin their Webs. — Early in the spring of 1866, while arrangements 

 were making for photographing a live male of the Nephila plumipes (the so-called 

 "silk spider of South Carolina"), the spider, after having several times traversed the 

 circle of wire on which it was, suddenly stopped, took a firm position at the top of the 

 frame and lifted the abdomen, poiuting it towards a large skylight which occupied the 

 middle of the ceiling: a slender shining thread was seen to shoot forth from the 

 spinnerets which occupy the end of the abdomen ; it seemed to have a blunt rounded 

 extremity, which advanced through the air rather quickly for a few inches, but after- 

 wards more slowly and steadily, and with an upward tendency, but always in the 

 direction of the skylight. When it had reached the length of five or six feet, 

 I allowed it to become attached to my coat; the issue ceased at once, and the spider, 

 having attached the end of the line, turned about and began to pull upon it. I now 

 bruke it off near the wire, and, believing that there was a current of air toward the 

 skylight, I blew gently upon the spider from various directions, and found that it 

 always pointed its abdomen in the direction in which I blew, and that the thread 

 was emitted in the same direction. So that while it seemed to have the power of 

 projecting a thread for a short distance, yet it always availed itself of the prevailing 

 current of air. — B. G. Wilder, in the 'American Naturali^l' for June, 1868. 



