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    The scorpions

Top of Vaejovis spinigerus male :
Yeux médians Yeux latéraux Yeux latèraux Pattes Pattes Chélicères Pattes Pédipalpe Mains Mains Tergites Pédipalpes

The manus:

  • The manus of pedipalps (more commonly called chela or hand) are various kinds, more or less large, more or less smooth. They are useful in the determination of the various families and the sex.
  • The hand is composed of two parts, the tarsus or mobile finger and the tibia, or fixed finger. Of course it is with these articles that the scorpion catches its preys, but it also makes use of it like tool to dig, and even like shield to protect itself (Pandinus, heterometrus).

The pedipalps:

  • The pedipalps so called "maxillipedes" and more usually "pincer" are composed of 6 segments, namely: the coxa, the trochanter, the femur, the patella, the tibia (hand and fixed finger) and the tarsus (mobile finger).
  • They are especially used for seizing preys, maintaining them in order to prick them, and bringing them to the chelicera. They are also useful during the couplings, the male then seizes those of the female to proceed to the "promenade à deux" before fertilizing this one.
  • Lastly, the pedipalps are used by the scorpion during its displacements. The hands ahead, the scorpion palpates each obstacle very often met it is as that which it finds a passage or the surged entry of one.

The chelicerae:

  • The chelicerae are composed of three segments, the coxa, the tibia and the tarsus, and resembles to a pincer, but smaller.
  • They are mainly employed to shred and crush the preys in order to make them assimilable. Indeed, it is with these articles that the scorpion will mix enzymes which go pre-digest the useful parts, and just left with the end a pellet of what is not assimilable.
  • The position of some hairs, and the teeth's forms on the chelicera are used to differentiate the species.

The eyes

  • Scorpions have two kinds of eyes. Median eyes, always one pair, located at the top of the prosomal carapace (cephalothorax), and one at five pairs of lateral eyes, located on the side of the cephalothorax.
  • In general the scorpions have six eyes. Some cavernicolous species, have no eyes like, for example, Belisarius xambeui in France, Troglotayosicus vachoni in Ecuador or Sotanochactas ellioti in Mexico.

Sternites and tergites:

  • The plates dorsally bear the name of tergites, those ventrally are named sternites. In fact chitinous plates protect the body from the scorpion, a kind of all things considered shield. There is always 7 tergites and 7 sternites on the mesosoma.
  • In fact the hulls decorate these plates which interest the systematician in order to determine the species and thus to know to which family the specimen belongs.

The metasoma:

  • The metasoma, often called "tail" is always composed of 5 segments (or rings) articulated.
  • On these elements, one can find carinae very useful into systematic to determine species and family of the specimen. For some species, we can also determine the sex by comparing the length of the segments of the metasoma. Males have one much longer tail (Hadogenes, Centruroides, for example).
  • The last segment (5th) is very often longer than the others, it is at the end of this one that the telson is. Between the vesicle and the 5th segment, the anus of the scorpion is.

The legs:

  • The scorpions are Arachnida, they thus have four pairs of legs, contrary to the Insects which have three pairs of them and to the Crustacea which have 5 pairs of them.
  • Those are composed of seven segments: coxa, trochanter, femur, patella, tibia, basitarsus, and tarsus. With at the end, a pair of claws is.
  • The legs are used of course for displacement but also, for the female, to collect, during the birth, the pullus which leave the genital opening (birth basket). They are also very useful to dig, the shifted action of the 8 legs also makes it possible to evacuate sand or the ground out of the burrow in construction.
  • We can as notice as the legs are a good indicator of the medium where the scorpion saw. Thus, the species digging of the burrows have legs shorter than the alive species in the rocks. The claws present at the end of the leg are much large, robust and hooked for the scorpions which climb on the trees or stones, that those alive on sand.

The telson:

  • The telson is composed of the vesicle and the aculeus. Its form, the presence of hairs (setae) on the telson, the presence of a tooth under the aculeus (the subaculear spine), but also the length and the curve of the aculeus, can help in the determination of the species.
Bottom of Vaejovis spinigerus male :

Chélicères Hanches Opercule génital Peignes Stigmate Stigmate Stigmate Stigmate Stigmate Stigmate Sternites


  • Under the cephalothorax is the coxa of the legs of the scorpion. It is the first element in the composition of those.

The genital operculum:

  • On the first sternite, is the genital operculum. It is made of two papillae which according to their form indicates the family, the kind or the species of the specimen. In some species these papillae are welded (Scorpionidae) and thus forms only one element.. It is necessary to raise this cover in order to reach the opening genital.
  • It is in this opening that one can find the "copulation hooks" of the male and thus allow to undoubtedly distinguish a male from a female. This operation is alas very delicate to practise and can be done only on dead specimens.

The pectines :

  • The pectines (or pecten) are specific to the scorpions. One finds them on the ventral face of the abdomen, on the second sternite, just below the genital operculum. They are two, of sizes and different forms according to the species and the sex.
  • These organ are chimico-sensory sensors which inform the scorpion about the ground, like its composition, its water content and its temperature. They are mobile organ, the scorpion makes use of it while scraping, to see in "palpating" surfaces to be determined.

The spiracles

  • There are 8 of them, the two first are hidden by the pectines.
  • They are the vestiges of the gills when the ancestors of the scorpion still lived in the sea.
  • They are on the sternites n° 3, 4, 5, 6. These are only small slits that muscles can open or seal according to the will of the scorpion. Behind these slits is the booklungs of the scorpion.


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