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The Influence of Relative Humidity on the Frequency of Clutches of 3 Forensically Important Blow Flies (Diptera: Calliphoridae)
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1  University of Windsor
Academic Editor: Kristopher Giles


Gravid females have numerous factors to take into consideration when choosing to lay eggs. The number of eggs laid per clutch compared to the number of clutches may impact the survival and fitness of her future offspring under conditions of varying temperature and humidity. Temperature and humidity interact to influence conditions of desiccation that may prevent eggs from successfully eclosing. The trade-off between clutch size and the number of clutches per female would be expected to vary under these conditions such that species more susceptible to egg desiccation should choose fewer and larger, compared to species that are less susceptible. Calliphora vicina Robineau-Desvoidy eggs are least susceptible to desiccation, followed by Lucilia sericata Meigen, with Phormia regina Meigen eggs as the most susceptible to desiccation, thus we expect P. regina females to lay the fewest, largest clutches compared to L. sericata and C. vicina. Individual females were released into an arena on a temperature gradient ranging from 10-40 °C under high (75-85%) and low (24-35%) relative humidity. Lucilia sericata laid either 1 clutch with 107 ± 10 eggs or 2 clutches of 50 ± 17 eggs. Both C. vicina and P. regina oviposited up to 3 clutches. Calliphora vicina laid 98 ± 24 eggs within 1 clutch, 55 ± 13 eggs when 2 clutches were oviposited, and 43 ± 12 when 3 clutches were laid. Lastly, P. regina laid 1 clutch of 86 ± 26 eggs, 42 ± 13 eggs when 2 clutches were oviposited, and 33 ± 4 eggs when 3 clutches were laid. Across all 3 species, clutch sizes ranged from 2-216 eggs per clutch. Despite our predictions, humidity did not affect clutch size (F1,86=0.1394, p=0.709), or the number of clutches laid (F1,86=0.2371, p=0.627). This suggests that each species has different oviposition strategies that impact their egg-laying behaviour.

Keywords: humidity; oviposition; clutches; number of eggs