First, I should mention that I am way backed up with ‘Ask and Entomologist’ questions from readers…so be patient with me as I get to them when I can. There are some good questions that have been asked so keep your eyes out.
Oran:
I was reading a blog the other day and the author mentioned trying to rescue a bee from a pool. He’d take it out, but it would keep on walking to the pool again and again. He wondered why he even bothered, seeing how bees are not sentient and what not. Well, that brought about a few questions. One: any ideas on why it kept going to the pool? Two: do you think insects like this can experience pain/suffering? Three: arthropods have ganglia instead of real brains, but I’m guessing they communicate with each other. Would you say the whole ganglial system is like one brain? and four: do arthropods have the same kinds of neurotransmitters (and used the same way) as humans do?
They’re probably difficult questions to answer (I remember people experimenting on lobsters to see if they felt pain, some concluding they do and others that they don’t), but a guess from an entomologist is better than my guess.
For those who may not know what sentient means, like I did at first, it refers to the ability to perceive or feel. To claim that insects do not have the ability to feel or perceive is a gross misjudgment, more about that in a sec though. I will answer the series of questions in order.
One: Why did the bee keep going in the pool? No idea. It could have something to do with the water surface reflectance looking like something else to the insect. A lot of insects look like bees, maybe it wasn’t a bee and an insect that was looking for a drink. A lot of times you see flies sucking up the rain water that collects on plants.
Two: 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. Vertebrates have nociceptors, which are specialized neurons that sense painful stimuli. Painful stimuli are described as noxious heat, mechanical or chemical stimuli that could potentially cause tissue damage. Tracey Jr. et al. (2003, sited above) found the following:
In models of nociception, noxious heat is often used as the stimulus to elicit a defensive motor output, as in the tail flick response of the rat. Since heat has also been shown to be an effective negatively reinforcing stimulus in adult Drosophila learning (Brembs and Heisenberg 2000 and Mariath 1985), we conjectured that heat might also be used to study nociception per se. A normal, undisturbed Drosophila larva moves through its environment with a rhythmic motion (Figure 1A). In response to light touch with a probe, a larva will pause (Figure 1B) or make one or more contractile waves, moving away from the stimulus (Kernan et al., 1994). In contrast, when touched with the same probe heated above a threshold temperature, larvae are seen to vigorously roll sideways in a corkscrew-like motion (Figure 1C). The threshold probe temperature for eliciting this behavior is 39°C–41°C (noxious heat), at which temperature several seconds of stimulation are required to induce rolling, but at 42°C or higher, the response occurs in as little as 0.4 s (Figure 1D). Importantly, the temperature threshold for firing of nociceptors in vertebrates, including primates, is similar, 39°C–41°C (Tillman et al., 1995). Since vertebrate nociceptors also respond to noxious mechanical stimuli (Beck et al. 1974; Bessou and Perl 1969 and Van Hees and Gybels 1981), we examined the response of Drosophila larvae to strong punctate stimuli or pinching of the cuticle with forceps, and these elicited the same rolling behavior as noxious heat.
But, like I said, there is some contention to the matter. Here is a nice little review on insect pain. If you don’t want to read the whole thing, below is an excerpt.
In the majority of examples of invertebrate nociception noted above, there seems to be little, if any, evidence that the animals’ responses persist in anything akin to the manner described for mammals. As Eisemann et al. (1984) have described in a review of the “biological evidence” concerning pain in insects, “No example is known to us of an insect showing protective behavior towards injured parts, such as by limping after leg injury or declining to feed or mate because of general abdominal injuries. On the contrary, our experience has been that insects will continue with normal activities even after severe injury or removal of body parts.”
Eisemann et al. (1984) use a variety of examples to support this contention, including:
* an insect walking with a crushed tarsus continues “applying it to the substrate with undiminished force”;
* a locust carries on feeding while being eaten by a mantis;
* a tsetse fly, although half-dissected, flies in to feed.
Although some insect behavior, such as the writhing of insects poisoned by insecticides, or the struggling of restrained living insects, resembles that of “higher animals responding to painful stimuli,” Eisemann et al. conclude that the resemblance is superficial and that it “no more requires the presence of a pain sense than do reflexive withdrawal responses.” Similarly, although it has been shown that fruit flies can be trained to avoid certain odors and colored lights when these are associated with impending electric shock (Quinn et al., 1974), such learning is open to explanation in terms of neural mechanisms, without the need to postulate subjective experience on the part of flies.
The “relatively simple organization” of the insect central nervous system, Elsemann et al. argue, “raises the question of whether any experience akin to human pain could be generated” in these animals (and by implication in other invertebrates with a similar or less complex nervous organization). On the analysis of Gould and Gould (1982), the answer to such a question would be “no,” for these authors can find no evidence for conscious experience in insects. Certainly, on the limited amount of evidence presented here, it seems very difficult to imagine that insects and the other simpler invertebrates mentioned above can “suffer” pain in anything like the vertebrate sense. Nevertheless, the issue certainly is not closed, and further questions should be asked.
Perhaps such a view simply reflects a paucity of (human) imagination. Griffin (1984) surely would urge us to maintain an open mind on the issue, having provided behavioral evidence which, he argues, should challenge “the widespread belief’ that an insect, for example, “is too small and its central nervous system too differently organized from ours to be capable of conscious thinking and planning or subjective feelings.” Indeed, to take a more radical view, perhaps “it is presumptuous for us to assume that because our suffering involves self-awareness, this should also be true of other species” (McFarland, 1989).
Alternatively, perhaps, as Mather (1989) suggests, we should simply accept that these animals “are different from us, and wait for more data.”
Three: Would you say the whole ganglia system is like one brain? Well actually, they do have a ‘brain’. Their central nervous system is made up of a double-chain of ganglia joined by lateral and longitudinal connectives. The ‘brain’ is the anterior ganglia and it is actually the fusion of 3 separate lobes (the protocerebrum, the deutocerebrum, and the tritocerebrum), collectively called the supraesophageal ganglion.
The connectives run next to the subesophageal ganglion, which is near the foregut. Posterior to the subesophageal ganglion is the thoracic ganglia (also sometimes called the thoracico-abdominal ganglion). These three ganglia make up the CNS.
Four: Do insects have the same kinds of neurotransmitters as humans do? A neurotransmitter is a chemical messenger that is released when a nerve impulse reaches the synapse. Yes insects have them and even more they have some of the same neurotransmitters as vertebrates do, such as serotonin, dopamine, and acetylcholine. Do they act similarly in insects as they do in vertebrates? Thats a great question and one in which I am a coauthor on a series of papers that are going through the review process right now (concerning octopamine and serotonin) in attempt to answer. I’ll wait to tell you more about that once the papers are published. But in short, I can say yes and no 
