Mr. J. Blackwall on the Structure, Functions 



instruments employed by male spiders in the propagation of their 

 species. 



Before they arrive at maturity spiders change their skin several 

 times : the manner in which these moults are effected may be illus- 

 trated by describing the proceedings of an individual of the species 

 £!peira calophylla. Preparatory to casting its integument, this 

 spider spins some strong lines in the vicinity of its snare, from which 

 it suspends itself by the feet and a filament proceeding from the 

 spinners. After remaining for a short time in this situation, the 

 coriaceous covering of the cephalothorax gives way laterally, dis- 

 uniting at the insertion of the legs and mandibles ; the line of sepa- 

 ration pursues the same direction till it extends to the abdomen, 

 which is next disengaged, the extrication of the legs being the last 

 and greatest difficulty the spider has to overcome. As the suspen- 

 sory filarnent connected with the spinners of the exuviae is consider- 

 ably shorter than the legs and does not undergo any sensible altera- 

 tion in length, the abdomen, during the process of moulting, be- 

 comes gradually deflected from its original horizontal direction till 

 it assumes a vertical position nearly at right angles with the cephalo- 

 thorax. By this change of posture, attended with numerous contor- 

 tions of the body, and alternate contractions and extensions of the 

 limbs, the spider is ultimately enabled to accomplish its purpose. 

 When it has completely disengaged itself from the slough, it remains, 

 for a short period, in a state of great exhaustion, suspended solely 

 by a thread from the spinners, connected with the interior of the 

 abdominal portion of the cast skin, which is much corrugated. After 

 reposing a little, the spider further attaches itself to the suspensory 

 lines by the claws of the feet, and when its strength is sufficiently 

 restored, and its limbs have acquired the requisite degree of firm- 

 ness, it ascends its filaments and seeks its retreat*. 



Recent observations establish the fact, that the number of times 

 spiders change their integument before they become adult is not 

 uniformly the same as regards every species. A young female 

 Epeira calophylla, disengaged from the egg on the 30th of March 

 1843, moulted on the 8th of the ensuing month in the cocoon, which 

 it quitted on the 1st of May ; moulting again, in the same year, on 

 the 4th of June, the 22nd of June, the 12th of July, and the 4th of 

 August, respectively, when it arrived at maturity, having cast its 

 skin five times. 



An egg of Epeira diadema, hatched on the 14th of April 1843, 

 produced a female spider, which moulted in the cocoon on the 24th 

 of the same month ; on the 3rd of May it quitted the cocoon, and 

 moulted again on the 21st of June, the 10th of July, the 3rd of 

 August, and the 23rd of August, in the same year. On the 28th 

 of February 1844 it died in a state of immaturity after having com- 

 pleted its fifth moult. 



On the 27th of June 1842 an e^^ of Tegenaria civilis produced 

 a female spider, which underwent its first moult in the cocoon on the 

 10th of the ensuing July ; quitting the cocoon on the 21st of the 



* Transactions of the Linnaean Society, vol xvi. p. 482-484. 



