Prolonged matings in a ladybird, Menochilus sexmaculatus: A mate guarding mechanism?

• Mating duration of less than 1 min produced deformed eggs.
• Mating duration from 1 to 2.50 min produced inviable eggs.
• Fecundity increased up to 30 min (min.) of mating duration.
• Egg viability increased in 3-cycles, i.e. 3-spermatophores transfer during mating.
• No reproductive enhancement beyond 30 min affirms mate guarding in this ladybird.

Occurrence of postcopulatory mate guarding behavior is common in those insects where males directly defend their partners from rival males, avoid sperm competition and thus increase their paternity success. However, this has not yet been evaluated in ladybirds (Coleoptera:Coccinellidae). In the present investigation, mate disruption studies were conducted to establish postcopulatory mate guarding behavior in a ladybird, Menochilus sexmaculatus (Fabricius). The laboratory findings affirmed the presence of mate guarding in this ladybird species. Results revealed significant influence of mate guarding behavior on fecundity and egg viability of females. The findings of the present study revealed that an effective mating took a minimum duration of 2.50 min, and prior to which sexual activities of a male were not effective to fertilize the eggs of a female. The results further demonstrate that males improved their paternity with a mating duration of above 4.50 min, while fecundity increased with a mating duration of above 4.75 min. Although fecundity increased continuously with an increase in mating duration from 4.75 min to 30.00 min, the egg viability increased with a mating duration of above 4.50 min and up to a duration of 10.00 min. For this reason, M. sexmaculatus males display postcopulatory mate guarding behavior after 30.00 min, and mate partners remaining in copula with the male riding on the female's back with his aedeagus inserted.

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