Volume 39, Number 1,
October 1992:
Springtails

Text-only version

ABOUT THIS ISSUE
- about KSN
- about the author

IN THIS ISSUE
- part 1
- part 2
- part 3
- part 4
- part 5
- part 6
- part 7
- part 8
- part 9
- part 10

SLIDESHOW
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Springtails
by Kenneth Christiansen

Figure 14. Sexual behavior in Sminthurides aquaticus; A) male grasping female antennae, b) close up of lock of male antenna on female, C) mating dance.

Most Collembola are bisexual, but the human meanings associated with that term are hardly appropriate. Males deposit sperm packets or spermatophores which are picked up by females which encounter them, and the sexes do not recognize each other. However, some members of the family Sminthuridae have elaborate courtship and spermatophore transfer techniques. For example, males of the genus Sminthurides, most of which live on water surfaces, have elaborate grasping antennae (Figure 14B) which they use to seize the female antennae. In some cases a pair may remain together for long periods of time with the female carrying the usually much smaller male suspended above the surface or every upside down on her back as is shown in Figure 14A. Periodically, in response to unknown cues, the male is lowered to the water surface. He deposits a spermatophore, and then guides the female to bring her genital opening into contact with it, whereupon the spermatophore ruptures and the female takes up the sperm. Another complex pattern is seen in the genus Bovicornia. Here the male has highly specialized structures on the forehead (Figure 15B) which he moves back and forth over the female's head (Figure 15A). This stimulates the female and the male turns around and secretes a sperm droplet (Figure 15C). The female picks it up with her mouth, deposits on the ground and then turns around and pushes it into her genital opening as shown in Figures 15D and E. Other members of the family have even more complex sexual activity. The members of this family are usually brightly colored and patterned; this is very probably associated with species and sex identification.

Another adaptation found in some Collembola is parthenogenesis where eggs do not need to be fertilized to develop and only females exist. This is found in Folsomia candida (shown in Figure 3). In this species most populations are parthenogenetic but some populations have both males and females. Other forms, particularly those found in caves or in deep soil layers where the chance of contact between the sexes is low, have species which are always parthenogenetic. For the deep soil forms of genus Tullbergia (Figure 16), almost all species are parthenogenetic.