The vast increase in the number of people studying one aspect or another of collembolan life in the past ten years has made'it essential that we bring together our knowledge of the bionomics of this group. The present review is an attempt to do this, and to offer some suggestions for future investiga tions in the area. Although the term "bionomics" has been used in a variety of ways, it is here considered to include studies of development and of the effect of various environmental factors on the organism, and the general ecology of the group. Publications concerned with soil zoology in a general way have not been included, except where they are of unusual importance for an understanding of the bionomics of Collembola. Even within these limits, a good deal of selection has been exercised, and the bibliography is in no way an attempt to present all the literature in the field, The last general review of the topic under consideration was that of Paclt (165), and for this reason I have concentrated on the publications since 1955.
LIFE CYCLES
SEXUAL MECHANISMSIt is clear at the present time that most, and probably all, Collembola accomplish fertilization by a sperm packet transfer mechanism [Sharma (196); Schaller (190,191,192)J. In an extensive study, Mayer (136) de veloped a classification illustrative of the different types of processes to be found: (a) simple sperm drop produced independent of the presence of other individuals and without direction (Onychiuridae) i (b) stalked droplet pro duced as above but with the possibility of an increased rat e of deposition in the presence of a mate (Orchesella, Tomocerus, Entomobrya); (c) stalked drop let produced in an undirected fashion but requiring the presence of a suitable female (Dicyrtorna and Allacma); (d) single droplet but with deposition and pick-up closely controlled [Sminthurides aquaticus (Bourlet) and Podura aquatica (Linnaeus)].In some cases, partial control of the process may be achieved by the fact that the male tends to eat old spermatophores [Mayer (136)]. Early observa tions by Lemoine and Lie-Pettersen of males smearing their mouth-parts wi th sperm and inserting these into the genital opening of the female must remain in doubt, because these actions have not been observed since that time, even