The EGG has been more extensively studied in Lepidoptera than in any other Order of Insects. It displays great variety: we meet with elongate forms (Fig. 164) and flat forms like buttons, while in _Limacodes_ (Fig. 83, Vol. V.) the egg is a {322}transparent scale of somewhat inconstant outline. Some are coloured and mottled somewhat after the fashion of birds'-eggs; this is the case with some eggs of Lasiocampidae and Liparidae; in some the sculpture of the egg-shell is of the most elaborate character (Figs. 77, 78, Vol. V.). The egg-shell or chorion is, according to Korschelt[182] and others, a cuticular product of the epithelium of the egg-chambers of the ovaries. The number of eggs deposited by an individual differs greatly in different species, and has been ascertained to be variable within certain limits in the same species. Speyer thought about 250 to be the average number of eggs deposited by an individual. The number in the case of _Aporia crataegi_ is believed to be from 60 to 100, and in some _Hepialus_ to be several thousands. The mode of deposition also differs greatly; where the eggs are very numerous they seem to be discharged almost at random in suitable spots; but moths such as _Clisiocampa neustria_ fasten their eggs round the stems of the food-plant in a very perfect and artistic manner. Butterflies seem as a rule to prefer to oviposit by placing an egg here and there rather than risk many in one situation; but to this there are many conspicuous exceptions especially in the cases where the larvae live gregariously, as in the Vanessae. Some moths cover the eggs with fur from their own body, which, in the case of certain of the Eggers (Lasiocampidae), seems to have a special supply for the purpose. The period that intervenes between deposition and hatching of the eggs varies from a few days to many months. There seems to be, as a rule, comparatively little power of extending the period of latency beyond a single season; though certain facts have been recorded that would lead us to believe that in Australia eggs may last over the proper time during a drought, and be hatched as soon as rain falls. [Illustration: Fig. 164—Egg of Orange-tip butterfly, _Euchloe cardamines_, magnified. _a_, The egg of natural size on a stalk.]