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Title: Developmental times and life tables for shore flies, Scatella tenuicosta (Diptera: Ephydridae), at three temperatures

Author
item UGINE, TODD - CORNELL UNIVERSITY
item SANDERSON, JOHN - CORNELL UNIVERSITY
item Wraight, Stephen

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2007
Publication Date: 10/1/2007
Citation: Ugine, T.A., Sanderson, J.P., Wraight, S.P. 2007. Developmental times and life tables for shore flies, Scatella tenuicosta (Diptera: Ephydridae), at three temperatures. Environmental Entomology. 36:989-997.

Interpretive Summary: The shore fly, Scatella tenuicosta, is an important nuisance pest in greenhouses and is also implicated as a vector of plant pathogens. Larvae and adults feed on algal mats that grow on wet greenhouse surfaces. This habit makes these insects difficult to rear, and consequently, their biology has not been thoroughly studied. Objectives of the present research included development of rearing and handling techniques and application of these methods to increase our knowledge of shore fly biology. An efficient rearing system employing Petri dishes with algae-infested filter paper disks was devised, and using this system, development of eggs, larvae, and pupae, and longevity and reproduction of adult shore flies were studied at three constant temperatures: 20, 26 and 28.5 deg C. Duration of the third (ultimate) larval stage ranged from 3.3 days at 20 deg C to 1.4 days at 28.5 deg C and was 1.7 - 1.9 times longer than the approximately equal first and second larval stages. Development of male and female shore flies from egg to adult required an average of 14.5, 8.2, and 7.0 days at 20, 26, and 28.5 deg C, respectively, and required an estimated 154.4 degree days. At these respective temperatures, female shore flies lived 21.8, 19.9, and 15.0 days, and produced 379, 710, and 477 eggs, respectively. Generation time and population doubling time were shortest at 28.5 deg C and were 12.4 and 1.6 days, respectively. This information is needed for comprehensive evaluation of the biological control potential of shore fly natural enemies, including parasitic wasps and fungal pathogens, whose effective use requires identification of vulnerable life stages and consideration of pest population growth statistics.

Technical Abstract: Development times and survivorship of immature shore flies, and longevity and reproduction of adult shore flies, Scatella tenuicosta Collin, reared on algae-infested filter paper, were studied at three temperatures (constant 20, 26 and 28.5 deg C) via life table analysis. The development time for each individual life stage as well as the total time from egg to adult decreased with increasing temperature. Duration of the third (ultimate) larval instar ranged from 3.3 more/less than 0.09 days at 20 deg C to 1.4 more/less than 0.04 days at 28.5 deg C and was 1.7 - 1.9-times longer than the approximately equal first and second instars. Development of male and female shore flies from egg to adult required an average of 14.5 more/less than 0.13, 8.2 more/less than 0.05, and 7.0 more/less than 0.04 days at 20, 26, and 28.5 deg C, respectively, and required an estimated 154.4 more/less than 1.2 thermal units. At these respective temperatures, adult females lived 21.8 more/less than 2.2, 19.9 more/less than 2.4, and 15.0 more/less than 1.4 days, and produced 379 more/less than 62, 710 more/less than 119, and 477 more/less than 83 eggs during oviposition periods of 14.3 more/less than 2.1, 15.0 more/less than 2.2, and 10.8 more/less than 1.4 days; daily lifetime egg production averaged 16.3 more/less than 2.3, 33.5 more/less than 3.8, and 29.7 more/less than 3.5. Results suggested that 26 deg C was near optimum for reproduction. Developmental stage-specific mortality was relatively low for all life stages at all temperatures, with maximum percent mortalities of 5.7% occurring in both the egg stage and in the third instar. The highest net reproductive rate (Ro) was obtained for insects reared at 26 deg C and was 329.6. The intrinsic rate of natural increase (rm) was highest at 28.5 deg C, and was 0.430. Generation time and doubling time of the population were shortest at 28.5 deg C and were 12.4 and 1.6 days, respectively.