Hilara sp. (Diptera: Empididae; Empidinae): Mating System, Swarm Movements, and Inbreeding Avoidance
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In a study spanning parts of nine years, an undescribed species of Hilara Meigen was observed to form mating swarms displaying complex behaviors. Typically, swarms were shaped like a flattened torus rotating rapidly about a horizontal axis. Many swarms also moved up and down and turned slowly back-and-forth about a vertical axis. Both up-and-down and turning movements were random in extent and direction, suggesting that they might arise as random, asymmetric density fluctuations within the swarms themselves. A rotating secondary swarm appeared intermittently inside one end of some primary swarms. Swarm membership changed continually as flies left one swarm to join another and as entire swarms coalesced. At one site the set of all swarms displayed properties not found in the swarms individually: spatial extension, daily dissipation and reconstitution over a period of weeks or months, reproductive potential, and gene flow. Such emergent properties qualify the set as a multicomponent swarm, an object heretofore known only in computer models. Hilara sp. appears to be protandrous, univoltine, and promiscuous. Generally, males paired preferentially with somewhat smaller females, but some small and medium-sized males paired with much larger females. Although males of nearly all known Hilara species present nuptial gifts of prey or other items to females, nuptial gifts were not observed at any time during the present study. Many characteristics of swarms of Hilara sp. can be understood as adaptations that reduce inbreeding.
KeywordsHilara rotating swarms multicomponent
I thank Jeffrey Cumming, Agriculture and Agri-Food Canada, for determining that submitted specimens represent an undescribed species of Hilara and for contributing numerous helpful comments on early drafts of the manuscript. Thanks are also due to Brian Brown, Natural History Museum of Los Angeles County, for his helpful comments on an early draft; to Richard E. Davis, University of San Francisco (ret.), for help with statistical questions; and to Linda McLaughlin for assistance in preparing the figures.
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Conflicts of interest
The author declares that he has no conflicts of interest.
- Carron A (2007) Correlation between wing measurements and dry body weight in male and female Ochlernotatus (Ochlerotatus) caspius (Pallas, 1771) (Diptera: Culicidae). Eur Mosq Bull 24:4–8Google Scholar
- Cohen IR, Harel D (2007) Explaining a complex living system: dynamics, multi-scaling and emergence. Royal Soc Inter. https://doi.org/10.1098/rsif.2006.0173
- Deguet J, Demazeau Y, Magnin L (2006) Elements about the Emergence Issue: A survey of emergence definitions. ComPlexUs, Inter J Mode Syst Biol, Soc, Cog and Info Sci 3(1–3):24–31Google Scholar
- Grootaert P (2004) Insecta: Diptera, Empididae. In: Yule CM, Yong HS (eds) Freshwater Invertebrates of the Malaysian Region. Malay Acad Sci, pp 805–809Google Scholar
- Kimura K, Hirano T, Chiba S (2014) Assortative mating with respect to size in the simultaneously hermaphroditic land snail Bradybaena pellucida. Acta Ethol (online), NovemberGoogle Scholar
- Kirby W, Spence W (1823) Letter XVI. Societies of Insects. In: Kirby W, Spence W, An Introduction to Entomology: Elements of the Natural History of Insects, vol. 2. Longman, Hurst, Rees, Orme, and Brown, London, pp 1–25Google Scholar
- Lynch M, Walsh B (1998) Genetics and Analysis of Quantitative Traits. Sinauer Associates, SunderlandGoogle Scholar
- Olson RS, Hintze AFC, Dyer FC, Knoester DB, Adami C (2013) Predator confusion is sufficient to evolve swarming behaviour. J Roy Soc Inter 10(85). https://doi.org/10.1098/rsif.2013.0305
- Reinhardt K, Naylor R, Siva-Jothy MT (2011) Male mating rate Is constrained by seminal fluid availability in bedbugs, Cimex lectularius. PLoS 11:2011: https://doi.org/10.1371/journal.pone.0022082
- Svensson BG, Petersson E (1987) Sex-role reversed in courtship behavior, sexual dimorphism and nuptial gifts in the dance fly, Empis borealis (L.) Entomol Fenn 4:323–334Google Scholar