Grassi informs us that these Insects are not uncommon under stones in Catania; they require moisture as well as warmth, but not too much; sometimes there is only one individual found under a stone, at others eight or ten. In the winter and spring their galleries are found on the surface of the earth, but in the hot months of summer they secure the requisite amount of moisture by sinking their galleries to the depth of ten or fifteen centimetres. Their food consists chiefly of vegetable matter. They may be reared with ease in glass vessels. Other species of the family attain wings; the details of the process are not well known. _Oligotoma michaeli_ (Fig. 222) was discovered in a hothouse in London among some orchid roots brought from India, and was found in more than one stage of development; the young greatly resemble the adult, except in the absence of wings. A nymph-form is described by M‘Lachlan[281] as possessing wings of intermediate length, and Hagen has suggested that this supposed nymph is really an adult female with short wings. If this latter view be correct, nothing is known as to the mode of development of wings in the family. It is still uncertain whether female Embiidae ever possess wings. Wood-Mason and Grassi have shown that there are wingless females in some species, and we know that there are winged males in others, but what the usual relation of the sexes may be in this respect is quite uncertain. These Insects have been detected in various parts of the world. In the Sandwich Islands _Oligotoma insularis_ was discovered by the Rev. T. Blackburn in the wood and thatch forming the roofs of natives' houses. A species has been found in Prussian amber, and Grassi thinks that _Embia solieri_—one of the Mediterranean species—is not to be distinguished with certainty from the Insect found in amber. Embiidae still remains one of the most enigmatic of the families of Insects. Although Grassi's recent observations are {355}of great value from an anatomical point of view, they rather add to, than diminish, the difficulties we encounter in endeavouring to understand the lives of these obscure creatures. That Embiidae form webs has long been known, and it was thought by some that the webs, like those of spiders, might be of assistance in procuring food. We may, however, infer from Grassi's observations that this is not the case, but that the silken tunnels or galleries—as he calls them—serve chiefly as a means of locomotion and protection, the feet of the Insects being highly modified in conformity with this mode of life. Grassi seems to be of opinion that the galleries are also useful in preserving a proper degree of humidity round the Insects. We have already alluded to the mystery that surrounds the mode of growth of their wings. Nearly all that is known as to the Embiidae is contained in Grassi's paper, or is referred to in Hagen's monograph of the family.[282]