590 



NA TURE 



\_Aprii 2 1, 1887 



DO SCORPIONS COMMIT SUICIDE ? 



/"CORRESPONDENTS of NATURE have repeatedly 

 ^ raised the question whether there is any truth in the 

 old legend that a scorpion, when placed within a ring of 

 red-hot embers, will, aftermaking futile efforts to pass the 

 fiery circle,deliberately kill itself by inflicting a wound with 

 a sting in its own head. Surgeon-General Bidie, of Madras 

 (vol. xi. p. 29), Dr. Allen Thomson (vol. xx. p. 577), and 

 Mr. Gillman (vol. xx. p. 629), have answered the question 

 in the affirmative. The other side has been taken by Mr. 

 Hutchinson (vol. xxi. p. 226), Mr. Curi'an (vol. xxi. p. 325), 

 and Mr. Lloyd Morgan (vol. xxvii. p. 313). Mr. Hutchin- 

 son maintained that the animals experimented on by Mr. 

 Gillman had died from excessive heat. To this Mr. Gill- 

 man replied, that the temperature in the centre of such 

 a circle of glowing charcoal as he used does not exceed 

 50" C. 



The subject has lately been thoroughly investigated by 

 Mr. Alfred G. Bourne, Professor of Biology in the Presi- 

 dency College, Madras ; and the results of his observa- 

 tions have been set forth in a paper communicated to the 

 Royal Society by Prof Ray Lankester. Some of the 

 details of his experiments are not very pleasant reading, 

 but it must be remembered that the question is one of 

 considerable importance, because, if it could be proved 

 that the scorpion commits suicide, its impulse to do so 

 would be, as Mr. Romanes has pointed out, " a unique 

 case of an instinct detrimental alike to the individual and 

 to the species." 



One of the arguments used to disprove the existence of 

 the supposed instinct is, that it is physically impossible 

 for a scorpion to sting itself in a vulnerable place. Mr. 

 Bourne shows that this statement is inaccurate. If, 

 he says, a dead scorpion be taken which is quite limp 

 and not in a state of rigour, it will be easily seen that the 

 last four segments of the tail are about the only portions 

 of the body, whether on the dorsal or ventral surface, 

 where a scorpion could not sting itself. Further, if two 

 fighting scorpions be watched, it will be seen that the 

 ectent to which the sting can be moved about is perfectly 1 

 wonderful. Moreover, he has noticed that, when the 

 scorpion is placed in very unpleasant circumstances, it 

 not unfrequently lashes its tail about and causes actual 

 penetration of the sting. If, for instance, the rays of 

 a burning-glass be concentrated on any part of the 

 body, the scorpion brings its sting there, and tries 

 to strike away the source of irritation. Occasion- 

 ally its efforts become more and more frantic, and the 

 point of the sting catches somewhere. The scorpion, 

 however, does not die unless the heat is concentrated on 

 the back. In that case it soon succumbs, even if the 

 sting has been tied down or previously removed. 



The moit important of Mr. Bourne's propositions is 

 that the poison of a scorpion is quite powerless to kill the 

 same individual, or another individual of the same sp;cies, 

 or even scorpions of other species. If this proposition is 

 established, there can, of course, b; no further controversy 

 about the matter. A priori, it is not improbable, for Sir 

 Joseph Fayrer has shown that the cobra poison will not 

 affect a cobra. Mr. Bourne frequently took a scorpion 

 in his hand, and, holding the sting between a pair of 

 forceps, pricked the scorpion with the sting and squeezed 

 out its poison. There was a little bleeding from the 

 wound, but in every case the scorpion lived for days. He 

 also tried stinging one scorpion with another, using in the 

 first instance specimens of the same species, then speci- 

 mens of different species. Occasionally, he thinks, the 

 stung indixidual became a trifle sluggish, but it never 

 died from the stmg. In order to make sure that his 

 method of squeezing out the poison was perfectly eflective, 

 Mr. Bourne, after stinging a scorpion, sometimes con- 

 tinued to hold the sting, and, taking a cockroach, squeezed 

 out into it some more of the poison. The cockroach in- 



variably became very sluggish at once, and died in an 

 hour or so. He also used a large cricket, stinging it in 

 the femur of the large hind-leg ; that leg became para- 

 lysed. When the animal was stung in the same placj on 

 both sides, both the hind-legs became useless, and it 

 crawled away on the two anterior pairs of legs. Stung in 

 the thorax it became quite torpid ; when placed on its 

 back it was not able to turn over. After considerable 

 search, Mr. Bourne procured some specimens of Thely- 

 pho?!iis, which he chose as being the nearest relatives of 

 the scorpions. He stung these in his usual method, and 

 in each case they died within six seconds. He then tried 

 some spiders, and they died in a few minutes when well' 

 stung. The slower general action in cockroaches and 

 crickets is probably, he supposes, to be explained by the 

 very inefficient circulation of the blood in insects as 

 compared with Arachnida. 



In all cases of artificial stinging Mr. Bourne took 

 especial care to avoid mechanical injury to the ner^^e ■ 

 ganglia. And he tried puncture without the introduc- ■ 

 tion of scorpion poison. Using large insects for this 1 



purpose, he obtained complete freedom from ill effects 

 when using simple puncture, whereas the same species of 

 insects when punctured with introduction of scorpion 

 poison were instantly paralysed, and died in half an hour. 

 He also procured two small shore crabs. One he punc- 

 tured between two joints of the great chela of one side ; 

 several drops of blood exuded, but they coagulated, and 

 the crab remained well. The second he stung in the 

 same place with scorpion's sting, squeezing it to insure 

 poisoning. The claw was immediately paralysed, and 

 the crab gradually became torpid, and died in less than 

 an hour. 



When a number of scorpions are kept together in cap- 

 tivity, it is not difficult to induce a couple to fight. Mr. 

 Bourne isolated such a couple, and they fought on and off 

 for two days, during which time each repeatedly stung the 

 other. On another occasion he separated two scorpions 

 which had been fighting, and which had repeatedly stung 

 one another. They lived perfectly well. 



Apropos of Mr. Gillman's remarks about the actual 

 temperature to which the scorpion is subjected in the 

 " fiery circle," Mr. Bourne tried this experiment. He 

 placed a scorpion and a cockcroach (tor comparison) in 

 an incubator with glass sides, and gave them a piece of 

 wood to walk about upon, and gradually raised the tem- 

 perature. At 40° C. both seemed uncomfortable, and the 

 cockroach performed a sort of licking action on all its 

 legs and antenna?. At 45' C. the scorpion became very 

 sluggish, and at 50" C. it was nearly dead. A large 

 furious scorpion before the experiment, it now lay on its 

 back and did not attempt to get up. Mr. Bourne took it 

 out and gave it a cold bath, and put it in a cool earthen- 

 ware vessel, and in the course of two hours it recovered. 

 The cockroach was left in the incubator till the tempera- 

 ture reached 52' C. When nearly dead, it was taken out, 

 and very gradually recovered. To try the eft'ect of a wet 

 heat, a scorpion and a cockroach were placed in water at 

 43" C., and they both died almost immediately, whereas 

 they would both have lived in cold water for hours. 



The inference drawn by Mr. Bourne from his experi- 

 ments is that scorpions do not commit suicide, and that 

 when they die within a ring of fire, heat is the cause of 

 death. After he had reached this conclusion he was told 

 that according to some authorities inclosure in a circle of 

 oil, or inclosure under an inverted tumbler, will cause a 

 scorpion to kill itself. He accordingly placed a scorpion 

 on a plate within a ring of cocoa-nut oil. It calmly walked 

 through. He placed another scorpion on a plate, and 

 round the edge a thick roll of rag dripping with kerosene 

 oil. The animal walked out over the rag. When daubed 

 with oil, it appeared uncomfortable, but did nothing 

 remarkable. The experiment with an inverted tumbler 

 was made, and gave the same negative result. 



