History of the star: This star is at the tip of the tail of the Scorpion and right on the sting. 

Lesos is Greek for sting, Latin, punctura scorpionis. The Arabic spelling for Lesath or Lesuth is Al-Las'ah (1). "The Stinger" of the Scorpion Scorpius, which, with lamda (Shaula), it marks.

Lamda (Shaula) and upsilon (this star Lesath) were the Arabic 17th manzil, Al Shaulah, and the Hindu nakshatra Vicritau, "the Sting", or "the Two Releasers"; perhaps from the Vedic opinion that they brought relief from lingering disease. Some Hindu authorities, taking in all the stars from epsilon to upsilon, called the whole Mula, the "Root", with the divine Nirrity, Calamity, as regent of the asterism, which was represented as a Lion's Tail; this title appearing also for stars of Sagittarius.

In Coptic Egypt lamda (Shaula) and upsilon (this star Lesath) were Minamref, "the Sting"; and, on the Euphrates, Sarur.

Iota, kappa, lamda (Shaula), theta (Sargas) and upsilon (this star Lesath), were the Girtab of the Euphratean lunar zodiac, the Vanant of Persia and Vanand of Sogdiana, all meaning the "Seizer," "Smiter," or "Stinger "; but the Persian and Sogdian words generally are used for our Regulus.

In Khorasmia these stars were Khachman, the Curved.

[Star Names, Their Lore and Meaning, Richard Hinchley Allen, 1889].

The astrological influences of the constellation: The Scorpion is associated with the Hebrew letter Oin and the 16th Tarot Trump "The Lightning-Struck Tower". (Robson*).

The astrological influences of the constellation given by Manilius:

"The Scorpion presides over arms" [Manilius, Astronomica, 1st century AD, book 4, p.253]

By virtue of his tail armed with its powerful sting, wherewith, when conducting the Sun's chariot through his sign, he cleaves the soil and sows seed in the furrow, the Scorpion creates natures ardent for war and active service, and a spirit which rejoices in plenteous bloodshed and in carnage more than in plunder. Why, these men spend even peace under arms : they fill the glades and scour the woods; they wage fierce warfare now against man, now against beast, and now they sell their persons to provide the spectacle of death and to perish in the arena, when, warfare in abeyance, they each find themselves foes to attack. There are those, too, who enjoy mock-fights and jousts in arms (such is their love of fighting) and devote their leisure to the study of war and every pursuit which arises from the art of war. [Manilius, Astronomica, 1st century AD, p.239-240]. 

The general astrological influences of the star: It gives danger, desperation, immorality and malevolence, and is connected with acid poisons. (Robson*). 

In close conjunction with lamda Scorpio Shaula, both in the 'Tail end of the Scorpion', has a Mars nature blended with Mercurian influence. According to tradition, Lesath in conjunction with Mars, Uranus or Saturn, MC or Ascendant could point to danger from wild animals, either to be ripped up by them, massacred, or torn into pieces. This medieval interpretation is no longer correct in these days.  At present, a configuration involving this star points to accidents, catastrophes, or operations. Corresponding to the sign Scorpio, this could work with appendicitis, appendectomy, or removing of hemorrhoids by operation. If associated with a benefic stellar body and if channeled in the right direction, there is the possibility that the energy associated with the Mars nature can make for marked achievements. (Fixed Stars and Their Interpretation, Elsbeth Ebertin, 1923)

Not unexpectedly it gets a Mercury-Mars rating from Ptolemy, what else for deft and swift injector like this?  Its qualities in the horoscope are very much those of a probing, sharp intellect and incisive wit, every bit as damaging as a knife to its opponent. It is one of the three Scorpio stars in Sagittarius which can be held to account for the often surprising bite in the otherwise genial, jovial Sagittarian (other stars in the tail of Scorpio; Aculeus and Acumen). It does show them to have an enterprising spirit of keenness of insight, not always thought of in connection with that religio-philosophical ninth sign of the zodiac. People with star strong in their charts are noted for doing well in debate, business, sport, and high office in general. If not well aspected, though, they can be inclined to strike first and ask afterwards, with an embarrassing loss of face. (The Living Stars, Dr. Eric Morse). 

References

*(Fixed Stars and Constellations in Astrology , Vivian E. Robson, 1923)