Insects will continue with normal activity even after sustaining a severe injury or removal of body parts. They do not limp when a leg is injured, they don't grasp an injury, they don't show signs of distress, when being eaten alive. When observing insects, they seem unaffected by things that should cause them great distress.
Decapitated insects will still execute normal behavior. A horsefly, will even copulate, after being deprived of its head.” Drosophila flies live for several days completely normally without a head: they will fly, walk and copulate.
I believe they do feel some sort of stimuli which helps them to determine hazardous situations to avoid, but I don't think it is suffering or distress, but a reaction genetically preprogrammed through millions of years of evolution.
As I said previously I "Personally" don't think insects feel pain, this is just my opinion. Derived from the evidence out there, and my personal experiences.
Pain = an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.
International Association for the Study of Pain (IASP)
The insect nervous system differs greatly from that of higher order animals. Insects lack the neurological structures that translate a negative stimulus into an emotional experience.
Pain is more than the stimulation of nerves. In fact, the IASP notes that patients can feel and report pain with no actual physical cause or stimulus. Pain is a subjective and emotional experience. Our response to unpleasant stimuli is influenced by our perceptions and past experiences.
I respect your opinions and I think we should be pushing for a lot more research in this area, to get a better understanding.
Far as lobsters go, If you are prepared to kill and eat it. Why are you so concerned on how you kill it, its going to die against its will anyway? If you really cared you wouldn't kill them in the first place.