Scientific eveidence is mounting showing that insects may have the ability to feel pain, which is an essential component of their survival.
If you spot an injured insect, don't just walk by to leave him or her to suffer. Quickly squish him to prevent future suffering.
Check out the scientific facts here:
• From “Ask An Entomologist: Can an insect percieve its surrounding or feel pain?”:
Do insects experience pain? Yes. Well actually, this concept has been disputed, but I think recent evidence suggests that they do experience what is defined as pain.
• References on this page note that substance P, a neurotransmitter causing pain in humans, has been found in fruit flies. This post (link now broken) states that some insects share some mammalian-type neurotransmitters, like serotonin, dopamine, and acetylcholine. And earthworms have endorphins.
• From Joan Dunayer's Speciesism (p. 128):
In any case, abundant evidence indicates that all invertebrates with a brain can experience pain. Like vertebrates, numerous invertebrates produce natural opiates and substance P. These animals include crustaceans (e.g., crabs, lobsters, and shrimps), insects (e.g., fruit flies locusts, and cockroaches), and mollusks (e.g., octopuses, squids, and snails).
Also, crustaceans, insects, and mollusks show less reaction to a noxious stimulus when they receive morphine. For example, morphine reduces the reaction of mantis shrimps to electric shock, praying mantises to electric shock, and land snails to a hot surface.
• Thomas Eisner and Scott Camazine, “Spider leg autotomy induced by prey venom injection: An adaptive response to 'pain'?”:
Field observations showed orb-weaving spiders (Argiope spp.) to undergo leg autotomy if they are stung in a leg by venomous insect prey (Phymata fasciata). The response occurs within seconds, before the venom can take lethal action by spread to the body of the spiders. Autotomy is induced also by honeybee venom and wasp venom, as well as by several venom components (serotonin, histamine, phospholipase A2, melittin) known to be responsible for the pain characteristically elicited by venom injection in humans. The sensing mechanism by which spiders detect injected harmful chemicals such as venoms therefore may be fundamentally similar to the one in humans that is coupled with the perception of pain.
Learning, Memory, and Motivation
A 1986 paper, “Invertebrate Learning and Memory: From Behavior to Molecules,” reviewed studies on a number of invertebrates, including bees, slugs, molluscs, snails, leeches, locusts, and fruit flies. The conclusion included the following remarks (pp. 473-76):
The progress achieved over the last 10-15 years in studying a wide variety of forms of learning in simple invertebrate animals is quite striking. There is now no question, for example, that associative learning is a common capacity in several invertebrate species. In fact, the higher-order features of learning seen in some invertebrates (notably bees and Limax) rivals that commonly observed in such star performers in the vertebrate laboratory as pigeons, rats, and rabbits.
[... W]e have reason to hope that the distinction between vertebrate and invertebrate learning and memory is one that will diminish as our understanding of underlying mechanisms increases.
• Georgia J. Mason, “Invertebrate welfare: where is the real evidence for conscious affective states?”:
[...] jumping spiders (Portia spp.) plan routes towards their prey ; and hermit crabs (Pagurus berhnardus) show evidence of motivational trade-offs during shell choice . Furthermore, if their brains are implanted with electrodes, garden snails (Helix aspersa) will learn to displace a lever, an action new to their behavioural repertoire, to stimulate those neural regions involved in sexual behaviour . None of these represent concrete evidence of conscious emotion, but they at least suggest that if cephalopods are to now be protected across Europe, then arachnids, decapod crustaceans and gastropods should be too.
• “For stressed bees, the glass is half empty”:
"We have shown that the emotional responses of bees to an aversive event are more similar to those of humans than previously thought," said Geraldine Wright of Newcastle University. "Bees stressed by a simulated predator attack exhibit pessimism mirroring that seen in depressed and anxious people."
But, they say, that isn't the same as saying that bees consciously experience emotions in the way that we do. On that point, the jury is still out.
In response to Edge's World Question Center 2005 topic, “What Do You Believe Is True Even Though You Cannot Prove It?”, Alun Anderson, Editor-in-Chief at New Scientist, made the following remarks:
Strangely, I believe that cockroaches are conscious. [Moreover,] I believe that many quite simple animals are conscious, including more attractive beasts like bees and butterflies.
What I mean by consciousness is] the feeling of “seeing” the world and its associations. For the bee, it is the feeling of being a bee. I don't mean that a bee is self-conscious or spends time thinking about itself. But of course the problem of why the bee has its own “feeling” is the same incomprehensible “hard problem” of why the activity of our nervous system gives rise to our own “feelings.”
But at least the bee's world is very visual and capable of being imagined. Some creatures live in sensory worlds that are much harder to access. Spiders that hunt at night live in a world dominated by the detection of faint vibration and of the tiniest flows of air that allow them to see fly passing by in pitch darkness. Sensory hairs that cover their body give them a sensitivity to touch far more finely grained than we can possibly feel through our own skin.
And as for the cockroaches, they are a little more human than the spiders. Like the owners of the New York apartments who detest them, they suffer from stress and can die from it, even without injury. They are also hierarchical and know their little territories well. When they are running for it, think twice before crushing out another world.
• A 2007 Discover Magazine article quotes Bruno van Swinderen:
Many people would pooh-pooh the notion of insects having brains that are in any way comparable to those of primates. But one has to think of the principles underlying how you put a brain together, and those principles are likely to be universal. Attention is a whole-brain phenomenon. A thing is not purely visual, not purely olfactory. It's a binding together of different parts that for us signify one thing. Why couldn't the fly's mechanism [of attention] be directed to a succession of its memories? That, to me, is just a short hop, skip, and a jump away from what might be consciousness.
And Christof Koch:
We have literally no idea at what level of brain complexity consciousness stops. Most people say, 'For heaven's sake, a bug isn't conscious.' But how do we know? We're not sure anymore. I don't kill bugs needlessly anymore. Probably what consciousness requires is a sufficiently complicated system with massive feedback. Insects have that. If you look at the mushroom bodies, they're massively parallel and have feedback.
In his 1984 Animal Thinking, Donald Griffin presents complex behaviors on the part of various species of insects that he feels suggest consciousness. He concludes chapter 5 with the remark (p. 116):
Explaining instinctive behavior in terms of conscious efforts to match neural templates may be more parsimonious than postulating a complete set of specifications for motor actions that will produce the characteristic structure under all probable conditions. Conscious efforts to match a template may be more economical and efficient. [Of course] it is not necessary to suppose that animals [including insects] are consciously aware of all their neural templates; perhaps only a few are important enough that the animal thinks consciously about them and considers alternative ways of realizing them.
On p. 105, Griffin elaborates an example:
The workers of leaf-cutter ants are tiny creatures, and their entire central nervous system is less than a millimeter in diameter. Even such a miniature brain contains many thousands of neurons, but ants must do many other things besides gathering leaves and tending fungus gardens. Can the genetic instructions stored in such a diminutive central nervous system prescribe all of the detailed motor actions carried out by one of these ants? Or is it more plausible to suppose that their DNA programs the development of simple generalizations such as “Search for juicy green leaves” or “Nibble away bits of fungus that do not smell right,” rather than specifying every flexion and extension of all six appendages?
Page 111 gives an example with spiders:
W. S. Bristowe (1976) describes how orb-weaving spiders sometimes vary their stereotyped behavior in dealing with small insects caught in their webs. If an experimenter holds a struggling fly with forceps close to such a spider, she omits the earlier stages of normal behavior (running along the web to reach the fly) and bites it immediately. If the fly is already dead, she wraps it in silk without biting it first. In constructing their elaborate webs, spiders are often said to follow a rigid series of behavior patterns which are presumably instinctive since a female spinning her first web does so almost perfectly. But she will make some alterations in structure when the surrounding vegetation or the space to be spanned is irregular. Bristowe describes how a spider whose web is ordinarily symmetrical builds a highly asymmetrical web when the opening between leaves makes such a shape appropriate. At the web's hub from which strands of silk radiate out to the surrounding vegetation, the spider ordinarily leaves a hole so she can quickly move from one side of the web to the other when an insect strikes it. In one web this hole, instead of being at the center, was close to one edge of the opening between the leaves of a lilac bush, and the strands formed a semicircle instead of a circle.
Many ethologists dismiss variability in structures such as spider webs as meaningless “noise” in a basically invariant system and deny that a spider could consciously adjust the structure of her web according to the shape of the available opening. But the end results are so efficiently adapted to their function of catching small flying insects that it seems possible that spiders anticipate the likely results of their web spinning.
• In his 1987 piece, “The moral standing of insects and the ethics of extinction,” Professor Jeffrey Lockwood, an entomologist and philosopher, summarizes arguments for self-awareness based on social interaction:
Another theoretical consideration of insect consciousness, is an extension of the work by Humphrey (1978) (who derived his work from that of Jolly (1966)) on the evolution of societies (Griffin 1984). The basic concept states that a critical step in the evolution of animal societies is the establishment of efficient interactions, and these interactions depend on group members' abilities to understand each others' thoughts, intentions, and feelings. Therefore, social insects must correctly judge the frame of mind, as it were, of one another.
Social insects behave so as to meet the communicated needs of the colony. One can construct a system which awkwardly explains social interaction such as food begging and tropholaxis or behaviors such as grooming, without including self-awareness. However, few would argue that social insects, and probably all insects, demonstrate an awareness of outside events; they behave according to environmental conditions and, as discussed earlier, they demonstrate the ability to communicate information about these conditions. Allowing that an insect has awareness of external events but does not have self-awareness is somewhat ridiculous--it is rather implausible to contend that through sensory mechanisms an insect is aware of the environment, other insects, and the needs of conspecifics but through some neural blockage, the same insect is selectively unconscious of sensory input about itself.