According to Grassi[[280]] there are ten pairs of stigmata, two thoracic and eight abdominal; these are connected by longitudinal and transverse tracheae into a single system. The ganglia of the ventral chain are, one suboesophageal, three thoracic, and seven abdominal; these are segmentally placed, except that there is no ganglion in the fifth abdominal segment. There is a stomato-gastric system but no "sympathetic." Salivary glands are present. The stomodaeal portions of the alimentary canal are remarkably capacious; the stomach is elongate and slender, without diverticula; the Malpighian tubes are elongate and slender; they vary in number with the age of the individual, attaining that of twenty in the adult. The ovaries are arranged somewhat after the fashion of those of Japyx, there being in each five short egg-tubes, opening at equal intervals into a straight duct. The testes are remarkably large; each one consists of five masses of lobules, and has a large vesicula seminalis, into the posterior part of which there open the ducts of two accessory glands. The large joint of the front tarsus includes glands whose secretion escapes by orifices at the tips of certain setae interspersed between the short spines that are placed on the sole.
Species of this genus occur in the Mediterranean region, but their characters have not yet been examined. Our information as to these is chiefly to be found in Grassi's work. The two species studied by him were wingless. They live under stones, where they spin webs by means of the front feet, whose first joint is, as we have said, enlarged and contains glands; the Insect uses the webs as a means of support in progression, acting on them by means of papillae and a comb-like structure placed on the four posterior feet.
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 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]]
Considerable difference of opinion has prevailed as to the allies of these obscure Insects. It would seem that they are most nearly allied to Termitidae and Psocidae. Grassi, however, considers these affinities only remote, and suggests that Embiidae should form a separate Order, to be placed in a super-Order Orthoptera, which would include our Aptera, the two families mentioned above, Mallophaga, Embiidae, and the ordinary Orthoptera. Brauer places the family in his Orthoptera genuina.
CHAPTER XVI
NEUROPTERA CONTINUED—TERMITIDAE, TERMITES OR WHITE ANTS
Fam. III. Termitidae—White Ants, Termites.
Fig. 225.—Termes (Hodotermes) mossambicus. Winged adult. (After Hagen.)