The uncertain symbolism of the three beasts–a leopard (or some other lithe, spotted animal), a lion, and a she-wolf–contributes to the shadowy atmosphere of the opening scene. Armed with information from later episodes, commentators often view the creatures as symbols, respectively, of the three major divisions of Dante’s hell: concupiscence (immoderate desires), violence, and fraud (though some equate the leopard with fraud and the she-wolf with concupiscence). Others associate them with envy, pride, and avarice. Perhaps they carry some political meaning as well (a she-wolf nursed the legendary founders of Rome–Romulus and Remus–and thus came to stand as a symbol of the city). Whatever his conception, Dante likely drew inspiration for the beasts from this biblical passage prophesying the destruction of those who refuse to repent for their iniquities: “Wherefore a lion out of the wood hath slain them, a wolf in the evening hath spoiled them, a leopard watcheth for their cities: every one that shall go out thence shall be taken, because their transgressions are multiplied, their rebellions strengthened” (Jeremiah 5:6).

It is perhaps best, at this early stage, to take note of the salient characteristics of the animals–the leopard’s spotted hide, the lion’s intimidating presence, the she-wolf’s insatiable hunger–and see how they relate to subsequent events in Dante’s journey through hell.

http://danteworlds.laits.utexas.edu/prologue.html

The beast in your quote represents concupiscence (immoderate desires).

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Cheers,

Bruce

Do these notes help? http://books.google.com/books?id=8lbk0Ikq1MAC&pg=PA31&lpg=PA31&dq=dante+inferno+she+mates+with+any+beast+and+will+mate+with+more+before+the+greyhound+comes+to+hunt+her+down+he+will+not+feed+on+lands+nor+loot+but+honor+and+love+and+wisdom+will+make+straight+his+way&source=web&ots=jZoSpOaDDa&sig=9wIJ92ZaQAkRvkxSxskT3jV74II#PPA33,M1