Characteristics of the ladybird Harmonia axyridis during autumn migration

Abstract: Sampling of the migrating ladybird beetle Harmonia axyridis (Coleoptera: Coccinellidae) on building walls was conducted between 5th October and 17th November 2009 in České Budějovice, Czech Republic. Out of 1571 individuals, there were 845 females and 726 males. The sex ratio in particular samples was even more strongly biased, suggesting infection of the ladybird population by male-killing bacteria. Mean female fresh weight was 37.3 mg, mean male weight was 30.8 mg. Mean weight significantly decreased during autumn, suggesting shortage of nutrients in later developing beetles. There were 56 individuals (3.6%) of morph conspicua (mean weight 32.7 mg), 156 individuals (9.9%) of morph spectabilis (mean weight 34.4 mg), and 1359 individuals (86.5%) of morph succinea (mean weight 34.3 mg). The proportion of melanic individuals was constant among samples. In later samples there were more individuals of the morph succinea that were heavily spotted. There were 46% of females fertilised before migration, regardless of colour morph. There was a slight decrease of fertilisation rate with later sampling date.