Behaviour and dispersal in adult Taeniopteryx nebulosa (Linnaeus, 1758) and Perlodes microcephalus (Pictet, 1833) (Plecoptera) in Denmark

ABSTRACT

Adult Taeniopteryx nebulosa (Linnaeus, 1758) and Perlodes microcephalus (Pictet, 1833) emerge late winter to early spring in Danish streams. Based on 13 years of study, we have provided new data and discussed little-known aspects of biology of these two species. Taeniopteryx nebulosa male deposits a spermatophore on the female gonopore. Both species are poor fliers and seek high posts for take-off, where they thermoregulate by basking in a pre-flight sun posture for heating flight muscles. Oviposition flight is erratic and short. The females skim back to land. Taeniopteryx nebulosa eggs drift a long distance as single eggs before adhering to vegetation. Perlodes microcephalus eggs drift a short distance as intact eggpackets before they fasten and disintegrate on the bottom. Perlodes microcephalus females select oviposition sites on or close to upstream a riffle. This is critical in ensuring that eggs fasten on stable gravel and stone bottoms. The fast recolonisation of P. microcephalus in Danish streams following restoration measures indicates efficient dispersal ability despite poor flight performance. Adults of both species adhere to clothes, feather and fur. Taeniopteryx nebulosa tarsomeres have many hooked setae, P. microcephalus tarsomeres have some hooked setae and a dense cover of microtrichia. They may disperse by hitchhiking on birds and mammals.

KEYWORDS:

• Plecoptera
• Taeniopteryx nebulosa
• Perlodes microcephalus
• microclimate
• thermoregulation
• spermatophore
• oviposition
• skimming
• hitchhiking
• Denmark

Acknowledgements

We thank Martin V. Sørensen, University of Copenhagen, for help with SEM photos, Flemming Sørensen, Ministry of the Environment, for distribution data, Jens Skriver for comments on distribution and dispersal, Vagn Brostrup and Tommy Wølk for graphic help, Steve Vogel, Duke University, for help with the biophysical matters, Jim Marden, Penn State University, Pennsylvania, and Armin Namayandeh, University of New Brunswick, for supply of information and linguistic help with the manuscript, Kellar Autumn, Lewis & Clark College, Oregon, for discussions on tarsal structures, and Arne Skovgaard Schmidt for a final polishing of manuscript grammar.

Disclosure statement

No potential conflict of interest was reported by the authors.