Cancer

Is one of the biggest constellations. In greek mythology, this constellation is in the sky because, while Hercules was fighting the goddess Hera, a crab appeared and bit Hercules’s foot,
then he crushed it. Hera wanted to immortalize the crab putting it in the sky.

If you want to locate it:

Cancer is a Northern Spring Constellation, so you can see it (if you are in the northern hemisphere) during spring. The best date to see it is at 21:00 in March. Cancer is composed of dim stars, so it must be a moonless night for your best chance to find it.

Look to the east and find Leo and Gemini. (These two Zodiac constellations are easier to find than Cancer, and they are a good guide because Cancer is located between them). Leo is marked by a backwards sickle, a collection of stars that form the lion’s head. Gemini contains two bright stars side by side (Castor and Pollux). Between them lies Cancer the Crab (even though, don’t expect to see a crab, because, the cancer constellation looks more like a faint upside-down letter “Y” and the stars that belong to this constellation are not very prominent). 
If you follow a line down through Gemini’s Pollux 
and Castor it will point to the Praesepe (also called Beehive Cluster), visible from the Earth as a fuzzy and hazy patch, it has about 350 stars in it. You can scan Cancer for one more feature, the smaller and fainter open cluster beneath the Praesepe. It will take a sharp eye even under the best circumstances to spot it, but the binoculars will enable you to see it as a fuzzy patch.