Monday, October 17, 2011

A Record of the Harlequin Ladybird in Cork City

Harlequin Ladybird, Harmonia axyridis f. spectabilis
One of the most imminent threats to native Irish species by invasives is the one the Harlequin Ladybird (Harmonia axyridis) poses to Irish native ladybirds. H. axyridis is larger and more aggressive than native Irish ladybird species and is thus able to out-compete them in hunting their preferred food of aphids. They also can have up to four generations per year, compared to the just one for native ladybird species and display less susceptibility to common diseases and parasites (1). Allied to this, H. axyridis also targets many non-aphid insect species, such as lepidopteran larvae and, most worryingly, ladybird larvae (2).
Harlequin Ladybird, Harmonia axyridis f. spectabilis
H. axyridis is native to Asia, specifically China, Japan, Korea, Mongolia and Siberia (1). Its voracious appetite for aphids marked it out as a seemingly effective biolocontrol agent and was introduced as such into the US in 1916. Establishment took some time but H. axyridis was recorded as such in 1988 and is now considered a pest there. Other than its effect on native ladybird populations, its tendency to overwinter in nooks and crannies in houses in quite large numbers make it a nuisance and may cause allergic reactions in inhabitants. Despite such problems, H. axyridis was inexplicably marketed as a biocontrol agent in mainland Europe in the 1990s. Commercial field releases first occurred in 1995 in France and was subsequently introduced as such in Belgium, Germany, Greece, Italy, the Netherlands, Spain, Portugal and Switzerland. H. axyridis has since spread to Austria, Luxembourg, Demark, Norway, Sweden and Great Britain, where it was first recorded in 2004 (3). The first Irish record for H. axyridis was in 2007 in Co. Down, with the first record for the Republic being in 2010 in Co. Wicklow (4). Another individual was recorded in 2010 in Cork City in November entering a house where individuals are wont to overwinter.
The individual pictured here was sighted entering a dwelling in the suburbs of Cork City on the 12th of October. Specifically, it was H. axyridis f. spectabilis that was sighted. This is the same variety that was seen in both records in 2010. Two other varieties are present throughout Europe, f. succinea and f. conspicua. H. axyridis is distinguished from other ladybird species by being noticibly larger, having red legs, being more domed than other species and may have a distinctive 'M' or 'W' mark on its pronotum (4).

  1. Brown et al., 2008. Biocontrol 53 pp. 5-21
  2. Rhule et al., 2010. Biological Control 53 pp. 243-247
  3. Roy et al., 2005. British Wildlife 16 pp. 403–407

No comments:

Post a Comment