ARACHNIDA. 309 



manclibulate insects to possess, we shall have good reason for surprise 

 in noticing the strange uses to which some parts of the oral appara- 

 tus are converted. In scorpions (fig. 140), the apparent repre- 

 sentatives of the mandibles of an insect are transformed into a pair 

 of small forceps, each being provided with a moveable claw ; these 

 therefore form of themselves prehensile organs adapted to seize prey, 

 and hold it in contact with the mouth. But it is in the maxilla 

 that we find the most extraordinary metamorphosis ; for the maxil- 

 lary palpi, so small in insects, are found to be developed to such 

 prodigious dimensions, that they far surpass in size and strength 

 any of the ambulatory extremities, and, from their resemblance to 

 the claws of Crustaceans, have given the character from which the 

 name of the division is derived.* Each of these formidable organs 

 is terminated by a strong pair of pincers, and thus the maxillary 

 palpi become converted into potent instruments either for attack 

 or defence. The representative of the labium of an insect in the 

 Arachnidans has no palpi connected with it. 



(355.) In spiders the organization of the mouth is altogether dif- 

 ferent. The mandibles (fig. 142, o, o) are each terminated with a 

 moveable fang (c), which ends in a sharp point, and is perforated near 

 its extremity by a minute orifice, from which, when the spider bites, 

 a venomous fluid of great potency is instilled into the wound in- 

 flicted ; such, indeed, is the malignity of this poisonous secretion 

 that its effects in destroying the life of a wounded insect are al- 

 most instantaneous, and in some of the large American species even 

 small birds fall victims to its virulence. The organ in which the 

 poison is elaborated is represented in the figure above referred to : 

 it is a long and slender bag, from which an attenuated duct may 

 be traced through the body of the mandible as far as the perforated 

 extremity of the fang. 



The palpi connected with the maxillse of the spider are termi- 

 nated in the female by a simple hook ; but in the males of many 

 species they exhibit a conformation slightly resembling the forceps 

 of the scorpion, although provided for a very different purpose. 

 When closed (fig. 141, B), the terminal part of the palpus pre- 

 sents a club-like dilatation, which, however, on close inspection 

 will be found to consist of several pieces (fig. 141, A, a,,c, </, e), 

 connected with each other by articulations, and capable of being 

 opened out in the manner represented in the figure. This strange 

 instrument was formerly imagined to be the penis of the male spi- 

 * Pes, a foot ; palpus, a feeler. 



