The Asian ladybird (Harmonia axyridis) ^{[Cuppen et al. 2015]} is omnipresent in the Netherlands ^{[Cuppen et al. 2015]} and in the garden, where it is one of the most common of ladybirds.

1. DISTRIBUTION

The Asian ladybird is an invasive species that has been introduced in 1996 as a biological control species to defeat aphids in greenhouses, and in fields of lettuce and arboriculture ^{[Cuppen et al. 2004]}. The reasoning was that the species could not survive the Dutch winters, but in 2002 it was first observed ‘in the wild’ ^{[Cuppen et al. 2004]}. According to Cuppen ^{[Cuppen et al. 2004]} it is probable that the species entered our country through Belgium where it was introduced earlier.

It is now one of the most abundant species of ladybird in the Netherlands and a threat to indigenous species. This is also true for most European countries in the area bordered by Great Brittain in the west, Denmark in the north, France and Italy in the south and Czech republic in the east. In southern countries like Spain, Portugal and Greece the species has been found but up to 2008 there was no sign of domestication yet ^{[Brown et al. 2008]}. I didn’t find more recent data on this.

2. BEHAVIOUR

2.1. FEEDING BEHAVIOUR

The fact that this species has been able to establish itself so quickly and managed to spread successfully throughout the country has to do with aspects of its behaviour. Like most other ladybirds it lives on aphids and is cannibalistic on the larvae of other ladybird species. What is different is that M. axyridis eat a lot more and has a diverse menu. Each day an adult beetle eats about 65 aphids, and about 5000 specimen of this or other species, during the period of 30 – 130 days during which it is active ^{[Majerus et al. 2006]}. It lives on aphids but as most other ladybird species the larvae are also cannibalistic on other ladybird larve. However M. axyridis is larger in size and more aggressive and has a higher win rate in encounters between species ^{[Raak-van den Berg 2012]}. Studies have shown that M. axyridis is more furtile, fecund and ferocious than Cycloneda sanguinea, a ladybird species in the US, and therefore outcompetes it ^{[Majerus et al. 2006]}.
They also eat the eggs and larvae of other insect among others butterflies (Monarch butterfly) ^{[Raak-van den Berg 2012]}.

A study ^{[Xue et al. 2009]}that compares the feeding behaviour on aphids by M. axyridis and the Seven-spotted ladybird (C. septempunctata), that other local ferocious predator in the garden, shows that both species consume about the same amounts per 24 hours. The data differentiates between feeding by the larva (third instar), the adult female and male. In both species the larvae and females eat the most and about the same amounts, and the males eat substantially less which can ascribed to the different nutrition needs for growing and reproduction.

The consumed number of prey depends among other on the total amount available. Below is an example (rounded) from the study ^{[Xue et al. 2009]} of the feeding ratio per 24 uur for larvae/females/males:

^luizen	^{C.septempunctata}	^M.axyridis
¹²⁰	^{82 / 90 / 61}	^{96 / 86 / 51}
¹⁸⁰	^{105 / 115 / 78}	^{112 / 95 / 54}

2.2. TOXICITY

Not only the hunting behaviour contributes to its succes but it turns out the species carries microsporidia, one celled parasites, whose spores are transferred to its eggs as well. A study suggests that when the larvae or eggs are eaten by other ladybird species those are fatally poisoned and die as they have lower tolerance to the parasite than M. axyridis ^{[Vilcinskas et al. 2013]}.

3. IDENTIFICATION

3.1. EGGS

The eggs are yellow but that is also the case in other ladybird species so not a unique characteristic.

Asian ladybird (*Harmonia axyridis*), laying eggs

3.2. LARVAE

INSTAR 4

4th instars are easily recognisable by the orange stripes on the edges of the abdomen.

Asian ladybird (*Harmonia axyridis*), 4th instar

3.3. PRE-PUPPA

Asian ladybird (*Harmonia axyridis*), prepupa

3.4. PUPPA

Asian ladybird (*Harmonia axyridis*), pupae

3.5. ADULTS

The species is large, 5 – 9 mm ^{[Cuppen et al. 2015]}.

Another characteristic of this species is the dent in the backside of the wing shields, a trait it shares in the Netherlands only with the Ten-spotted ladybird ^{[Cuppen et al. 2015]}.

Asian ladybird (*Harmonia axyridis*), characteristic dent in wing covers

3. IDENTIFICATION

M. axyridis has an enormous diversity in color schemes and dots. About 200 color variations have been described ^{[Tan 1945]} and up to nineteen dots on both wing shields ^{[Tan 1945]}.
These variations can be broadly defined in two categories ^{[Cuppen et al. 2015]}:

white neck shield with black dots or black dots connected in the shape of a black ‘M’, and red or orange wing shields with a variable amount of dots
black neck shield with broad white edges and black wing shield with one or two red dots