Monday, March 26, 2012

A Loveliness of Ladybirds*

A Loveliness of Seven-Spot Ladybirds, Coccinella septempunctata
The Seven-spot Ladybird (Coccinella septempunctata) is the most common species of ladybird present in Ireland, often quite abundant in areas. Adults are emerging, or have emerged, from hibernation at this time of year and will remain active until October (1). It is a species that is widespread throughout the palaearctic region, and its success is due to a high degree of ecological plasticity. It is a highly mobile beetle, and capable of thriving in a variety of different habitats (eurytophic). Its can also be considered polyphagous in its diet, with at least 24 species of aphid being counted as prey (2). Post emergence from hibernation, when aphid number are be quite low, C. septempunctata will feed on nectar and pollen from a variety of plants. Females can also suspend oviposition in the presence of already hatched larvae, which avoids any problems of cannibalism. When eggs are layed, an excess of offspring for the carrying capacity of local food resources often results, which allows C. septempunctata to take advantage of unpredicatably occuring aphid populations (2).
 
Evidence of eurytophy in Coccinella septempunctata: larvae on a sand-dune
While numbers of C. septempunctata remain high in Ireland, they may soon be under threat from the invasive Harlequin Ladybird (Harmonia axyridis) which can not only out-compete, but also feeds on C. septempunctata larvae. The breeding site for H. axyridis reported on this blog last year (but sighted in 2012) along with another from Co. Carlow are worrying developments.

*The title of this post comes from the collective noun for a group of ladybirds, a loveliness.

References:
  1. Sterry, 2004 Collins Complete Guide to Irish Wildlife p. 150
  2. Hodek and Michaud, 2008. European Journal of Entomology p. 1-12

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