pest

The snow peas that I sowed about 2 weeks ago had sprouted and I was very excited. Little did I knew that whatever pest it is in the soil was happy too. Looks as if that they have come out at night when nobody is watching and chew off anything green as soon as they appear. 

Does anybody know what kind of pest they might be? I see ants crawling around. Could they be the culprit? Wonder how I could eliminate them without using chemical pesticide? I sprayed some pepper on top of the soil, thinking that that might deter them, but NO!

Other plants in my garden are doing well. More rain would be nice though. I will post more photos next time.