Ladybirds in Harrow

The first map shows records of all species of ladybird in Harrow and the surrounding areas. There were few records before 2000 but now the area is well covered - mainly by members of the Harrow Natural History Society.

The most numerous ladybirds are the 2-spot and the 7-spot ladybirds. The next two maps show the frequencies (how often they have been recorded over the last five years) of these species which should be roughly proportional to their abundance. There are differences in distribution and abundance between the two species but these do not, yet, look too significant!

We might expect the 2-spot (Adalia bipunctata) to be found most often in more built-up areas and the 7-spot (Coccinella septempunctata) to be more common in larger, open green areas. Clearly more data and more analysis is required here.

Species list

The table shows the species which have been identified between 2000-2004, giving the numbers of records (observations per place per week) and the numbers of individuals.

Genus	species		Records	Individuals	Mean	Max
Adalia	bipunctata	2-spot	373	1040	2.8	43
Coccinella	septempunctata	7-spot	200	483	2.4	31
Psyllobora	vigintiduopunctata	22-spot	48	59	1.2	5
Propylea	quattuordecimpunctata	14-spot	26	38	1.5	7
Halyzia	sedecimguttata	Orange	24	34	1.4	9
Adalia	decempunctata	10-spot	18	18	1.0	1
Exochomus	quadripustulatus	Pine	9	10	1.1	2
Calvia	quattuordecimguttata	Cream-spot	8	8	1.0	1
Subcoccinella	vigintiquattuorpunctata	24-spot	4	5	1.3	2
Chilocorus	renipustulatus	Kidney-spot	3	3	1.0	1
Tytthaspis	sedecimpunctata	16-spot	2	7	3.5	6
Hippodamia	variegata	Adonis'	2	2	1.0	1
Anisosticta	novemdecimpunctata	Water	1	1	1.0	1
Myrrha	octodecimguttata	18-spot	1	1	1.0	1
All			719	1709

The abundances are largely in line with the findings across London with the exceptions of the pine, 10-spot and cream-spot ladybirds. These are arboreal species and the relatively low numbers reflect the predominance of gardens and open spaces amongst the observed sites.

However, the orange ladybird Halyzia sedecimguttata, also an arboreal species (it feeds on leaf mildews) is not uncommon. Until the turn of the century it had been a fairly uncommon species seen mainly in ancient woodland: the only old record comes from Stanmore Common. However since 1998 large aggregations (thousands of ladybirds) have occasionally been seen in spring and autumn while individuals are now seen elsewhere, presumably flying around in search of mildewed trees. The next map suggests that its centre of activity is in the woods to the north of the borough (and also in the Ruislip woods) but that it flies during the summer over a wider area.

Phenology

The next chart shows the frequency of three species (the percentage of each species in each calendar month) for the five year period.

The curve for the 2-spot is the most straightforward: over-wintered ladybirds emerge in March-April but become most active, along with the new generation during May-June. Numbers decline in August and the ladybirds hide away during the autumn to overwinter.

The 7-spot is more complex. It becomes active earlier in the spring but numbers seem to drop off during May, giving a June-July peak with relatively sustained activity to October. This might suggest that there is a greater separation between old and new generations than in the 2-spot.

This may be significant for ladybird mortality: a pathogenic fungus is transferred between ladybirds. This should largely die off with the old generation (the case in 7-spots) but where the generations overlap (as with these 2-spots) the fungus remains constantly present in the population.

To get more value from these maps I shall need to compare year with year: activity varies with the weather of course so combining many years may obscure these effects.

The orange ladybird distribution demonstrates that it remains active during the heat of summer and also that it has one activity peak before winter.