Buthus occitanus (Amoreaux, 1789)

Colombo, Marco, 2011, On Fabre’s traces: an important contributor to the knowledge of Buthus occitanus (Amoreux, 1789), Euscorpius 117 (117), pp. 1-10 : 4-8

: Buthus occitanus , female’s closeup lyriform carinae near eyes (photo by Colombo). Figure 3

showing

Marco white [butterfly] makes it escape just beating its amputated wings on the ground ” ( Fabre, 1905).

After various trials in order to find the right prey kind or size ( Fig. 7.1 ), he observed scorpion predation upon the beetle Omophlus lepturoides (Fabricius, 1787) ( Tenebrionidae : Alleculinae ), and then upon butterflies and other insects. During his nocturnal observations “at the light of the lamp”, Fabre begun finding cases of cannibalism among adults, that he immediately associated to a post-mating behaviour, as it happens in some praying mantids (however, he also observed cannibalism perpetrated by adults against juveniles; Fabre, 1905).

Fabre was also interested in the duration of fasting: in one of his experiments, he put four specimens in different jars without giving them any food, and they survived for about nine months without eating (from autumn to May-June); he assumed that they used their reserves to survive ( Fabre, 1905).

During his observations, Fabre underlined that, when attacking its prey, Buthus occitanus does not use its sting and venom, unless the prey is large, or it effectively tries to escape or defend itself; this is true also for other scorpion species (e.g. genus Euscorpius Thorell, 1876 ; M.Colombo, pers. obs.). The sting, according to Fabre, is mostly used for defense. In order to verify this, Fabre set up a small “arena” where he put scorpions together with big terrestrial spiders ( Lycosa narbonensis Walckenaer, 1806 ). He observed that pedipalps helped scorpions in blocking the opponents and keeping them away, while the sting was used to kill wolf spiders. The same experiment was made with praying mantids, which could be a prey of the scorpions when laying eggs in autumn under big stones, and also rhinoceros beetles, dragonflies, and many other insects ( Fabre, 1905). Nowadays, however, this kind of experiments would hardly be acceptable and would be neither useful nor informative, since Fabre conducted them in captivity conditions that had little in common with natural situations. However, these experiments were in line with Fabre’s concept of a naturalist: “ the naturalist interrogating beasts is inevitably a torturer; there is no other way to make them talk ” ( Fabre, 1905).

Particularly interesting were Fabre’s observations about reproductive behaviour in Buthus occitanus : these were the results of hours spent with the lamp near a big terrarium in the courtyard, sometimes together with other family members.

In April, the scorpions in his terrarium were very active, and Fabre often found cases of cannibalism ( Figs. 7.2 , 8 ), noticing, however, that those were the females (“ darker coloration, paunchy belly ”) eating males (“ pale coloration, belly less paunchy ”) and not vice versa, linking this phenomenon not to territoriality but to breeding aspects (this kind of cannibalism, however, does not apply always and to all scorpion species; Lourenço, 2002). In fact, he later observed that during the night many specimens formed couples. With his careful eye, Fabre described how the male takes the female from pedipalps and brings her to a shelter ( Fig. 9 ; the famous promenade a deux, in order to bring the female to a spermatophore placed before; Lourenço, 2002), and the moment in which the pair puts chelicerae and the frontal part of prosoma in contact, comparing it to a kiss (“ We say that dove invented the kiss, but it has a precursor: the scorpion ”). For many days, he attempted to see the exact moment of mating, but for many reasons (for example long duration of preliminary phases, late hour, tiredness, and rain) he could not observe this particular behaviour, and thought that scorpions mate in the same way as crickets ( Fabre, 1905).

Finally, Fabre succeeded in observing the most spectacular event of the courtship complex behaviour: the pair lifts tails together, undertaking a position called “ arbre droit ”: “ To declare his love ” he wrote “ the scorpion does the arbre droit ” ( Fabre, 1905).

In the end, the French entomologist also observed, during summer months, the birth of the offspring and their permanence on the mother’s back ( Fig. 7.3 ), making also experiments, such as transferring some juveniles from one female to another and verifying that they also accept offspring other than their own ( Fabre, 1905).

Conclusions

Jean-Henri Fabre has been one of the living examples of the fact that passion, combined with knowledge even if autodidactic, can lead to a huge amount of observations, data and interesting results. During his research of the “scientific truth”, he conducted experiments (notable the ones with moths in order to understand how females attract males; Fabre, 1930) and left to the scientific community very interesting data. With regard to scorpions, he observed many aspects of life history of the French Buthus occitanus . As he had wrote referring to his predecessors, “ the chisel of the masters revealed to us the organic structure [of the scorpion], but no observer, as far as I know, investigates its intimate habits. Gutted after alcohol maceration, it is very well known; active in the domain of its instincts, it is ignored. Nobody, however, would deserve more than it, among segmented animals, the details of a biography ” ( Fabre, 1905). Many things have changed since his publications: for example, new species belonging to this genus have been described from Iberian populations, previously thought to belong to B. occitanus (Gantenbein & Largiadèr, 2003; Lourenço & Vachon, 2004). Furthermore, the discovery of fluorescence in scorpion cuticle in 1954 has revolutionized the way of looking for and studying scorpion behaviour with the aid of UV lamps, without disturbing them ( Fig. 10 ; Lowe et al., 2003).

However, Fabre’s contribution to the knowledge of the most intimate aspects of the Languedoc yellow scorpion’s life is unquestionable and has to be recognized.

Figures

Figure 7: A plate from The Life of Insects, depicting predation, cannibalism and offspring in the Languedoc yellow scorpion. 1. Languedoc scorpion devouring a grasshopper. 2. After mating, the female eats the male. 3. The mother and her family ready for emancipation (after Fabre, 1920a).

Figure 8: Cannibalism can be observed in Buthus occitanus both in the field and in captivity (photograph by Marco Colombo).

Figure 9: Another plate from the same book, depicting courtship behaviour. 1. Initial courtship. 2. Promenade-a-deux. 3. The pair enters the nuptial hut (after Fabre, 1920a).

Figure 10: A Buthus occitanus under UV light (photo by Marco Colombo).