Editing Small tortoiseshell (section)

==Decline in population==
Once among the most common butterflies in Europe and temperate Asia, this butterfly is in very rapid decline, at least in Western Europe. This decline cannot be explained by the decline of its host plant, because the nettle is widespread and even enjoys the general [[Eutrophication#Terrestrial ecosystems|eutrophication]] of the environment. The [[chrysalis]] is sometimes eaten by wasps, but these are also in strong regression. The effect of other phenomena are still poorly understood ([[environmental degradation]], air pollution, contamination by pesticides). Scientific evidence shows that the summer drought is a cause of declining populations, because larvae grow normally on drenched leaves (but hatchlings were even rarer the wet summers of 2007 and 2008). However, before 2000, according to data from an English butterfly monitoring programme, there was a good correlation between reproductive success, the abundance of populations of this species and the host plant moisture stress. From 1976 to 1995, the butterfly had more success in summers that were cool and wet at the beginning of summer than when it was hot and dry. This butterfly may then be sensitive to global warming.

===Droughts===
The small tortoiseshell butterfly is severely affected by droughts. During periods of drought, the butterfly experiences a vastly reduced reproductive rate. The drought directly affects the ''Urtica'' leaves; the higher the nitrogen and water level in the leaves, the more rapid the growth of the larvae. During a drought, both of these levels drop significantly, leaving the tortoiseshell larvae nothing to feed on. The timing of rainfall is also a crucial factor. If there is not adequate rainfall in the early summer, then the plants will not be able to fully develop, leaving the larvae without a suitable source of nutrition. These butterflies actively produce smaller broods under these conditions.<ref>Pollard, E., and J. N. Greatorex‐Davies (1997) "Drought reduces breeding success of the butterfly ''Aglais urticae''." ''Ecological Entomology'' '''22''' (3) : 315–318.</ref>