322 Mr. J. Blackwall on the Structure ^ Functions 



with the feet of the hind-legs, and such also as they design to attach 

 themselves to*. 



There are on the superior part of the metatarsus of the posterior 

 legs of all the Ciniflonidce two parallel rows of moveable spines com- 

 mencing just below its articulation with the tibia and terminating 

 near its lower extremity. In a state of repose, the spines composing 

 both rows are directed down the joint and are somewhat inclined to- 

 wards each other ; those of the upper row have a considerable degree 

 of curvature and taper gradually to a fine point, those of the lower 

 row being stronger, more closely set, and less curved. Employed to 

 transform, by the process of curling, certain lines proceeding from 

 the spinners into the small flocculi characteristic of the snares of the 

 Ci7iiJlonidce, the double series of spines has received the name of 

 calamistrum. 



When a spider of this family purposes to form a flocculus, it 

 presses its spinners against one of the glossy lines constituting the 

 foundation of its snare, and, emitting from them a small quantity of 

 liquid gum, attaches to it several slender filaments, drawn out by 

 advancing the abdomen a little, and kept distinct by extending the 

 spinning mammulae laterally. The posterior legs are then raised 

 above the plane of position, and the tarsal claws of one of them are 

 applied to the superior surface of the metatarsus of the other, near 

 its articulation with the tarsus, and the calamistrum is brought im- 

 mediately beneath the spinners, at right angles with the line of the 

 abdomen. By a slight extension of the joints of the posterior legs 

 the calamistrum is directed backwards across the diverging extre- 

 mities of the spinners, which it touches in its transit, and is restored 

 to its former position by a corresponding degree of contraction in 

 the joints. In proportion to the continuation of this process the in- 

 flected lines of the flocculus are produced, the spider making room 

 for them as they accumulate by elevating and at the same time ad- 

 vancing the abdomen a little, which it effects by slightly extending 

 the joints of the third pair of legs and contracting those of the first 

 and second pairs. When the requisite quantity of inflected filaments 

 is obtained, the spider again applies its spinners to one of the glossy 

 lines and attaches the flocculus to it. In this manner it proceeds with 

 its labours, occasionally employing both calamistra^ till the snare is 

 completed. The modus operandi appears to be this. The points of 

 the lower row of spines in passing over the extremities of the spinners 

 draw from them lines which run into numerous flexures in conse- 

 quence of not being kept fully extended, and the purpose subserved 

 by the spines of the upper row is the detachment of these lines from 

 the spines of the lower row by a motion upwards f. 



If the metatarsus of one of the posterior legs of Ciniflo ferox, a 

 spider of frequent occurrence in the interior of buildings, be ex- 

 amined under the microscope with a moderately high magnifying 

 power, the arrangement of the spines composing the two rows which 

 constitute the calamistrum will be apparent. 



* Transactions of the Linnsean Society, vol. xvi. p. 476 ; vol. xviii.p. 224, note*. 

 t Ibid. pp. 471-475 ; vol. xviii. pp. 224, 606. 



