Voltinism and larval growth pattern in Coenagrion mercuriale (Odonata: Coenagrionidae) at its northern range margin

• Main Authors: Bethan V. PURSE, David J. THOMPSON
• Format: Article
• Language: English
• Published: Institute of Entomology, Biology Centre, Czech Academy of Science 2002-03-01
• Series: European Journal of Entomology
• Subjects: odonata; coenagrion mercuriale; pyrrhosoma nymphula; seasonal regulation; diapause; voltinism; larval growth; intraspecific predation
• Online Access: https://www.eje.cz/artkey/eje-200201-0004_Voltinism_and_larval_growth_pattern_in_Coenagrion_mercuriale_Odonata_Coenagrionidae_at_its_northern_range_ma.php
• ISSN: 1210-5759; 1802-8829

Voltinism and larval growth pattern were investigated in an edge-of-range population of Coenagrion mercuriale. Coenagrion mercuriale is semi-voltine in Britain and growth is inhibited in winter. The 2nd year group overwinters in a range of instars between the antepenultimate and final instar consistent with the early, asynchronous emergence pattern of this species. A facultative autumnal diapause in the penultimate instar is the most likely mode of seasonal regulation. The broad size distribution of larvae produced by this growth pattern was wider than that found in co-occurring populations of Pyrrhosoma nymphula, a "spring" species with synchronous emergence. The broad size distributions may lead to considerable intraspecific interference between C. mercuriale larvae. Sex ratio in the last three larval instars of C. mercuriale did not differ significantly from unity. A laboratory investigation of the effect of temperature and photoperiod on growth and diapause in C. mercuriale is recommended to determine whether high minimum temperature thresholds for development limit both the width of the temporal niche and microhabitat use by this species at its range margin.