Impulse patterns in the flight motor neurones of Bombus californicus and Oncopeltus fasciatus.

The ability of central nervous systems to generate complex patterns of motor output without patterned input has now been clearly established. Some of the most thorough analyses of such centrally generated patterns have been made on the flight-control mechanisms of locusts (see Wilson, 1967, for a review) and calliphorid flies (Wyman, 1966, 1969; Mulloney, 1969). Each of these studies included a description of the normal output from the thoracic ganglia to the flight muscles during flight, in terms of the activity of the individual motor neurones. The patterns described for locusts and other neurogenic fliers such as moths (Kammer, 1967) are similar, suggesting that similar mechanisms are operating in these orders. The patterns described in flies are so different from those of locusts and moths that they are probably the products of very different mechanisms. This difference raises the possibility of many unrelated mechanisms generating flight, each restricted to a small group of animals, each of which would have to be examined before any generality would emerge. This paper reports the results of a comparative study of the normal patterns of motor output to the indirect flight muscles during flight in Bombus californicus (Hymenoptera) and Oncopeltus fasciatus (Hemiptera). These species were chosen as representatives of two major orders of myogenic insects in the hope that the results would clarify the relation of the previously described dipteran motor patterns to those of the orthopterans and lepidopterans.