Is Karma different for accidental killing than intentional killing? Ever since I have started following Buddhism, I have stopped killing any type of insects but during the course of time I have accidentally killed few insects when I had no intentions of harming them like 
1) While using touchscreen a tiny insect of few millimeters in length came between my screen &amp; finger.
2) Accidental killing mosquito in sleep as they bite us.
3) Ants come under my feet whenever I am busy going from A to B (Here I mean totally immersed in work mode where you don't have time to think of anything else.

So is Karma different for such types of incidents because I never intent to harm such beings, forget about killing them or will I get the same punishment for intentional killing?
The background story to the first verse of the Dhammapada is of an arhat killing insects accidentally, because he's blind.

The verse says,


  All mental phenomena have mind as their forerunner; they have mind as their chief; they are mind-made. If one speaks or acts with an evil mind, 'dukkha' follows him just as the wheel follows the hoofprint of the ox that draws the cart.


I think we're meant to infer that if you don't act with an evil mind (or act without an evil mind), that if the killing is accidental or unintentional, that's not as bad as intentional killing.



Something similar is found in the monastic rules (page 29):


  In analyzing offenses for the purpose of determining penalties, the
  Vibhanga divides an action into five factors: the effort, the perception under which
  it is made, the intention motivating it, the object at which it is aimed, and the
  result. In some of the rules, all five factors play a role in determining what is and
  is not a full offense. In others, only two, three, or four play a role. For example,
  under the parajika rule forbidding murder, all five factors have to be present for
  a full offense: The object has to be a human being, the bhikkhu has to perceive
  him/her as a living being, he has to have murderous intent, he has to make an
  effort for the person to die, and the person has to die.
  
  If any of these factors is missing, the penalty changes. For instance, object: If
  the bhikkhu kills a dog, the penalty is a pacittiya (i.e. a less-severe penalty]. Perception: If he cremates a
  friend, thinking that the friend is dead, then even if the friend is actually alive but
  severely comatose, the bhikkhu incurs no penalty. Intention: If he accidentally
  drops a rock on a person standing below him, he incurs no penalty even if the
  person dies. Effort: If he sees a person fall into the river but makes no effort to
  save the person, he incurs no penalty even if the person drowns. Result: If he
  tries to kill a person, but only succeeds in injuring him, he incurs a thullaccaya [which is another less-severe penalty].