Joanna writes: Is the cockroachs brain spread around its body?
Joanna, Insects as a group are said to think in their periphery. This is because many of their innate behaviors are hardwired in peripheral ganglions more so than vertebrates. For instance flying behavior is controlled in the thoracic ganglia and some reproductive behavior such as copulation is controlled in the last abdominal ganglion. Whenever sexual behavior or flying behavior has to be coordinated with the visual system the behavior includes what you might call the brain (head ganglion). The standard cockroach escape mechanism involves the tail (cerci) sensory signals that impinge on the terminal abdominal ganglion (A6) and giant fibers that communicate an escape signal from A6 to the 3 thoracic ganglia (T1-T3) which control the legs in running behavior. So people might say that the cockroach’s brain is spread around the body in abdominal ganglia A1-A6 and thoracic ganglia T1-T3 and head ganglia (brain, frontal and suboesophageal ganglion).
