Butterfly eggs vary a lot in appearance from species to species; they are often beautifully sculptured, with spines, ribs, pimples and dimples, or with a honeycomb grating, and range in shape from spherical to flattened, resembling small lozenges, buttons, barrels, spindles, or domes! The usually pale colours often change towards hatching and may also be patterned by dots or splashes of another colour. You can see them in all their variety through a strong magnifying glass. (Map 01, Araschnia levana)

The number of eggs that are laid at a time also varies a lot between species. In most species, the female first looks for a suitable food plant. Some butterflies, such as the Purple Emperor, lay one egg at a time, looking anew for a place to deposit the next one. Other species lay the eggs in small to large batches, that may be unordered clusters, such as those of the Marsh Fritillary, or the two neat layers of the eggs of the Scarce Fritillary. The Map even attaches the eggs one to the other, forming small chains under the nettle leaves. However, there are some species, such as the Marbled White and Meadow Brown, where the female just lets her eggs fall in the vegetation, either when perched or in flight.

The eggs of most species are ripe within ten to fifteen days. They then hatch, the young caterpillar leaving the egg, sometimes making its first meal of the eggshell. (002.MOV, eggs and larvae of the Large White)
Some caterpillars even remain within the egg during the winter. However, the eggs of some species, such as those of the Brown Hairstreak, can become more than half a year old.