For most of us involved in some form of ecological research, it is an allconsuming task to ferret out sufficient empirical data to substantiate a pseudohypothesis, let alone attempting to keep abreast of the vast amount of current literature that is being published in one's own miniscule research department, particularly when the day-to-day routine of lecturing and working with graduate students lends little time for research and writing. It is, therefore, a matter of considerable satisfaction when a researcher in a particular field can not only add significant data through his own research but at the same time examine the mass of published data, bring it together, organize it, and present it to us in one mammoth volume. This the author has accomplished most fully and most effectively.
The subject of insect movement is, by its very nature, an extremely complex one because there exists a vast array of different types of movement complicated by the vagaries of weather conditions, food supply, host relationships, and so on. With respect to the wind factor insects may be moved by wind currents and carried to considerable heights without any directional control on the part of the insect. In this consideration, the author, having devoted most of his research to the movement of aphids, is of the opinion that winged insects occurring in the upper air are flying actively, and therefore, considers that the concept of passive buoyancy must be reconsidered. However, it has been maintained by certain workers in insect dispersal that the relative size, weight and buoyancy determined the height to which insects attained, particularly the higher altitudes from 6,000 to 14,000 ft. In reference to this the author believes this idea may be true only for inert particles or dead insects. However, since live insects have been taken or observed by investigators using planes or equivalent means in the free air, this conclusion given for small or weak flying insects as actively flying may not be valid, for it would be difficult to ascertain whether or not they are actively flying or were inert. Strong winds or convection currents are too forceful for any weak flying insect to resist, and could be readily carried along or upward regardless of their power of flight, and therefore the smaller and weaker insects could be considered as so much inert material carried in the air streams.
Most ecologists working in this field realize that many species of insects move deliberately and with little relationship to wind direction, as in the case of the monarch butterfly which, if one will permit an analogy to bird movement, may be termed a "true migrant" and not one depending on wind direction. As in the case of birds, weather conditions may affect direction to a limited extent but not the overall path of population flight.
To attempt to categorize insect movement into three classes of "migration"