Cydalima perspectalis

Eggs are 1 mm in diameter, located under green unattacked leaves. First larvae just coming out from the egg are about 1–2 mm long. Larvae development brings them in four weeks to about 35–40 mm at maximum. There is some shrinkage at the beginning of the nymphosis, pupae are 25–30 mm long, first green with browning longitudinal lines, then more and more brownish. The wingspan of the adult form is 40–45 mm. Two variants are observed, the most common one is mostly white while the other is most entirely light brown.

There are two or three generations per year with adults on the wing from April/May to September.. In the warmest parts of the European importation area, with cold conditions coming late in the year, there might be sometimes four generations per year. The species overwinters as a juvenile cocooned larva (about 5–10 mm long), protected in an hibernarium made of two leaving Buxus leaves solidly joined by silk.

Larval feeding damage - only the contour of the leaves and frass is left.

The larvae feed on the leaves and shoots of Buxus species.[14] Young larvae only eat the upper part of the leaf, leaving the hardest inside structure. The leaves are not destroyed completely but appear as "peeled" in small parallel beats lines, or almost completely. These peeled leaves eventually die. Old larvae are the most damaging: they massively and completely eat the leaves, sometimes leaving a thin part at the contour and centre of the leaf, however. Green ball-shaped frass can usually be seen on host plants.

Vespa velutina (Asian predatory wasp) in active search of Cydalima perspectalis larvae on an infested box-tree bush.

In the area of origin (Asia) natural regulation occurs, as witnessed by the non-destructive behavior of C. perspectalis. In the area of Europe where the moth has been introduced, the damage is very serious because natural regulation does not occur at a significant level. However, in European areas where the Asian hornet (Vespa velutina) is present prior to the introduction of C. perspectalis, some degree of predation by the wasp is observed (not confirmed by scientific and clear results). This is namely in the south-west of France, the first place where V. velutina was introduced to Europe in 2004 (C. perspectalis invaded this area in 2012). V. velutina is able to capture small larvae, and larvae preparing for the nymphosis in their cocoon. Where V. velutina has been introduced this causes other problems as it preys on honey bees and European honey bees are more vulnerable than their Asian counterparts. Further research is conducted for the suitability of C. perspectalis for parasitoid species, such as the tachinid Exorista larvarum[15].