XII HABITS EXTERNAL STRUCTURE 301 



and presently both would disappear into the newly -formed 

 retreat. 



After mating, the male was often devoured by the female. 

 Moreover, after any combat with an enemy, such as a Lycosa or a 

 Scolopendra, it appeared to be de rigiieur to eat the vanquished, 

 and on such occasions only was awj considerable amuunt of food 

 consumed. 



The scorpions were not, however, anxious to fight, greatly 

 preferring to retire if possible ; but wiien incited to combat, their 

 sting was quickly fatal to any mature insect, to spiders and to 

 centipedes. Curiously enough, Iiowever, insect larvae, though 

 badly wounded, did not succinnb to the poison. Newly-hatched 

 scorpions mounted on the mother's back, where they remained 

 motionless for a week, entirely unfed. They then underwent 

 a moult, after which they were able to forage for themselves. 



External Structure. 



The chitinous plates of the prosoma are fused to form a 

 carapace. Six segments are clearly indicated by the six pairs of 

 appendages, but, though the development of Scorpio affords little 

 direct evidence of the fact, there is reason to believe that there 

 once existed a pre-cheliceral segment,^ as has been clearly proved 

 in the case of the spiders. An embryonic pregenital segment 

 has also been recognised. The six prosomatic appendages are 

 those proper to the Arachnida, being the chelicerae, pedipalpi, 

 and four pairs of ambulatory legs. The mesosoma, which is 

 broadly attached to the prosoma, comprises six segments, in- 

 dicated ventrally by the genital operculum, the pectines, and the 

 four pairs of pulmonary stigmata. The last of the broad ab- 

 dominal segments, which tapers abruptly, belongs to the metasoma, 

 which also comprises six segments, and is succeeded by the 

 post-anal spine or sting. 



Prosoma. — Near the middle of the carapace are two median 

 eyes, and on its antero-lateral borders are usually to be found 

 groups of smaller eyes, numbering from two to five. All the eyes 

 are simple. There is a difference, however, in their development, 

 the median eyes being dii)lostichous, or involving two layers of 

 hypoderm, while the lateral eyes are monosticJioiis, and pass 

 through a stage strikingly like the Y)ermanent condition of the 

 ^ Brauer, ZeitscJir. wiss. ZooJ. lix., 1895, p. 355. 



