Overwintering

 BugBlog has been dormant for a few weeks. Somehow, posts somehow never went past the project status. But today, the sun shone after days of rain and gloominess, and in a walk at the park, my 4 year old and I did an informal ladybird survey. We checked many tree trunks and spotted lots of ladybirds, not as many Harlequins as other years, but still the easiest ladybird to find in the park. They were quite active as it was mild, and walked on the tree trunks in the sun. More than 40 in total, as the cluster of Harlequins above nestled in a little hole on a tree trunk was a little tricky to count. A single 2 spot ladybird completed the survey.

Forked tailed flower bee on common toadflax

I planted a new bed with native flowers earlier in the year: foxgloves, hedge woundwort, common toadflax, oregano and bird's foot trefoil. It has been very popular with bees and other insects, but there was the one plant that I hadn't seen being visited: the common toadflax, Linaria vulgaris. This relative of the snapdragon has spikes of closed flowers that require some effort for insect to access the nectar and pollen. On top of that, the flower has a very long spur which contains the nectar, so only long-tongued bees can reach the nectar - barring nectar robbers which will make a hole in the spur. The wait was worth its while, as last week, later than I have seen this species before, a female Anthophora furcata turned up and fed on all available flowers, collecting the pollen. She was also pollinating the flower, you might see the flower's anther pushing against the bee's head. The bee came back again the same day for another visit. She had large bare patches on the abdomen and thorax, but still showed the characteristic fringe of red hairs at the end of the abdomen. The flowers are beautiful, it is a native plant and it attracts one of my favourite bees, what else can one ask for?

UPDATE 20/09/12
Since writing this post, I have watched the long tongued bumblebee Bombus pascuorum visiting these flowers too.

Inside curly cherry leaves with their food

Yesterday we gave our cherry tree a light trim, removing shoot tips damaged by the black cherry aphid. The leaves curl up, sheltering hundreds of aphids (above). Inside the leaves, with their prey, there were hundreds of Harlequin larvae larvae, a few 2 spot larvae and with few adults of both species, a 10 spot ladybird and a few predatory hemipteran bugs.

A mirid bug Deraeocoris ruber (I think!)

10 spot ladybird, near a black cherry aphid

Fully grown Harlequin larvae

2 spot ladybird larvae

Two spot ladybird

An unusual 2 spot ladybird with 3 spots!

Cherry wars

The new shoots of my cherry tree are covered on Black Cherry Aphids, Myzus cerasi. The new leaves are stunted and folded, sheltering the aphid colonies which produce abundant honeydew - loved by bees and bumblebees. Ladybirds have also arrived at the tree in search of the aphids. There are many Harlequin ladybirds, mating, feeding and laying eggs (above).

Today, tens of Harlequin egg clusters were very obvious under the leaves...

...often close to aphid infestations. 

One of the clusters was already hatching: a new generation of Harlequins 

There were also many 2 spot ladybirds on the cherry, I am not sure they are as advanced on their life cycle as the Harlequin, although this pair was mating. Given the strong impact of Harlequins on 2 spot populations, it is obvious there is more than one war going on in the cherry tree. All the photos, except for the top one (26/05/12) taken today.

Ups and downs of ladybirds

I came across a 2 spot ladybird today on the way home (above, being checked by a garden ant). This ladybird species seems to have been the main loser in the Harlequin ladybird invasion, with a 44% decline since the harlequin arrived. They share habitat, and the small size of the 2 spot makes it easy prey of the harlequin when in the larval stage. The future does not bode well for the 2 spot. The same stretch of road where we found the lone 2 spot is a Harlequin hotspot: today there were tens of active harlequins, and we counted not one...

 not two...

 not three...

but five pairs mating.

Is global warming erasing a melanism cline?

 The 2 spot ladybirds, Adalia bipunctata, I find in my garden are of the typical morph, red with 2 black spots, one in the centre of each wing case, but there is also a melanic morph in this species* - black with four red spots - and several rarer intermediate morphs, which are determined genetically. Some colour morphs tend to be more common in some areas than in others. This geographic variation is thought to reflect differences in temperature regulation between morphs. Melanic ladybirds benefit from thermoregulating more effectively in certain microclimates: when there is little, intermittent sunshine and is colder. This advantage becomes most important in early spring, when after emerging from hibernation ladybird behaviour is strongly limited by temperature, so the black ladybirds can start reproducing earlier. Paul Brakefield and Peter de Jong have studied the polymorphism in the two spot ladybird in Holland for 30 years. The two spot colour polymorphism, nicely matched the differences in climate between the warmer coast and the colder inland areas. At the beginning of their study period, in 1980, the dark morph was commonest inland, where it reached 60%, and its frequency decreased gradually towards the coast (less than 20%). Samples taken in the same transect since then show how the sharp decline in frequency of the dark morph gradually disappeared to the point that there was little if no differences between sampled areas in 2004, with the frequency of the melanics in inland areas dropping to similar levels than the frequency in coastal areas. Brakefield and de Jong think that the disappearance of this cline is a response of the ladybirds to the gradually warming climate in the area.

Figure 1 Changes over time in the proportion of the illustrated melanic and non-melanic morphs of the two-spot ladybird beetle along a transect of ca. 115 km in length in the Netherlands (bottom-left). Samples were collected in each of the 5 years indicated at 16 more or less evenly spaced localities from west to east. Colouring of years matches the histograms for melanic frequency in the individual samples from each locality. The panel on the bottom-right shows deviations in average temperature from a ‘normal’ season/year at De Bilt (red spot on map). From left to right, columns represent data for winter (Wi), spring (Sp), summer (Su), autumn (Au) and the overall year (Tot), respectively, and from top to bottom for different years beginning before the period of ladybird sampling. The colour of each block indicates the extent to which the average temperature in the particular season/year deviated from ‘normal’; white, no deviation, blue, cooler than normal (dark blue more extreme than light blue), red, warmer than normal (dark red more extreme than light red)(from Brakefield & de Jong, 2011)

The story has a second dark aspect. The researchers had trouble reaching acceptable sample sizes in the 2004 sampling season. They even failed to find 2 spot ladybirds in two localities where they previously had been abundant. They attribute the decrease in numbers of the 2 spot ladybird to the impact of the invasive harlequin ladybird, which reached Holland in 2002. Not only the melanism cline is gone, but the 2 spot seems to be dissapearing as well.

References

Brakefield PM, & de Jong PW (2011). A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change? Heredity PMID: 21792220

*UPDATE
So it seems I do have melanic 2 spots in the garden (above). Thank you to Helen Roy, who curates the Ladybird survey site for the ID.