Predatory Efficiency of the Semi-aquatic Bug Microvelia douglasi Scott 1874 (Hemiptera: Veliidae) with a Note on Factors Influencing its Predatory Performance

Author: Subramanian Arivoli, Samuel Tennyson, Miriam Cecilia Vassou, Grace Marin, Elangovan Vigneshkumar and Raji Kalaivani

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Abstract

The present work centers on the predatory efficiency of Microvelia douglasi adults. To investigate the test hypothesis of this study, as well as density-dependent predation of Microvelia douglasi adults, this experiment was designed. Microvelia douglasi adults were categorized as predators, and all the larval instars of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus formed the prey. The first and second instar of the prey were categorized as ‘small prey’, while their third and fourth instar as ‘large prey’. The effectiveness of predation was investigated at prey densities of 25, 50, 75 and 100. Experiments were carried in six containers containing dechlorinated tap water wherein volume of three containers were 500mL and the volume of the other three containers were 1000mL. The predators (predator density of two) comprised of three categories (male, female, and both male and female) were introduced into the 500mL and 1000mL containers offered with each prey species separately of varied prey size. Control lacked predators to ensure mortality does not occur in any prey. All tests lasted for an hour only. Predation varied with regard to varied prey densities, however, maximum predation was at 25 prey density irrespective of prey species. The number of prey killed by Microvelia douglasi adults irrespective of their sex, prey size, and prey type varied. Highest successful attacks were noticed in female followed by male. Microvelia douglasi male and female adults preyed on 111.8 and 116.6 Aedes aegypti, 121.8 and 141.0 Anopheles stephensi, and 60.6 and 70.8 Culex quinquefasciatus, respectively, and their respective percentage of predation was 56.91 and 60.11; 53.26 and 62.13; 32.58 and 31.78. Prey consumed was high in I and II instars of all prey species, and predation was low as the prey death rate declined from III to IV instars, irrespective of the prey species. In Aedes aegypti, 237.8 and 104.0 number of small and large prey were consumed, while for Anopheles stephensi, it was 285.2 and 131.0, and in the case of Culex quinquefasciatus, it was 138.4 and 65.2, respectively, and their respective percentage of predation was 41.0 and 16.9; 42.7 and 21.0; 23.6 and 11.2. Amongst the prey types, Anopheles stephensi was more preferred, as they were found floating parallel to the water surface, and was easier to attack them, followed by Aedes aegypti and Culex quinquefasciatus. The total number of larvae predated by Microvelia douglasi adults in Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus were 341.8, 416.2 and 203.6, respectively.

Keywords

Microvelia douglasi, Aedes aegypti, Anopheles stephensi, Culex quinquefasciatus, predator-prey interaction, predatory performance, prey density, prey size, prey type

Conclusion

The current investigation portrayed the predatory performance of Microvelia douglasi adults governed by factors, viz., predator’s performance, irrespective of its, stage and sex, its prey recognition and capture, and by the type, size and density of prey.

References

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How to cite this article

Subramanian Arivoli, Samuel Tennyson, Miriam Cecilia Vassou, Grace Marin, Elangovan Vigneshkumar and Raji Kalaivani (2023). Predatory Efficiency of the Semi-aquatic Bug Microvelia douglasi Scott 1874 (Hemiptera: Veliidae) with a Note on Factors Influencing its Predatory Performance. Biological Forum – An International Journal, 15(4): 93-100.