Mouth usually masticatory; wings, four in number, all membranous, generally nearly equal in size, traversed by numerous delicate nervures, having a longitudinal and transverse direction, and giving them a reticulated, lace-like aspect. Metamorphosis generally incomplete, rarely complete. The larva active, hexapod, the pupa active or quiescent.
The order Neuroptera includes a number of Insects which are so different in their characters, habits, and metamorphoses, that they are sometimes placed in three separate and special groups. The first section includes what may be termed normal Neuroptera, such as the Ant-lions (Myrmeleontidae), the Aphis-lions (Hemerobiidae, fig. 185), the Scorpion-flies (Panorpidae), and the Sialidae. The second section includes the Dragon - flies (Libellulidae), the May-flies (Ephemeridae), the Stone-flies (Per/idee), the White Ants (Termitidae), and some less important families. These are often placed in the Orthoptera, under the common name of Pseudo-neuroptera. Lastly, we have a section sometimes elevated to the rank of a distinct order under the name of Trich-optera, for the reception of the singular Caddis - flies (Phrygatneidae). In this group the anterior wings are generally hairy, the mandibles are rudimentary, the larva usually resides in a case formed of small foreign bodies, and the pupa is inactive during the greater part of its life.
Fig. 185. - Neuroptera. Aphis-lion (Chrysopa perla), imago, larva, and eggs.
Amongst the more remarkable of the Neuroptera are the so-called "White Ants" or Termites, a brief description of which may be given here. The Termites are social insects, living in organised communities, and they are mostly inhabitants of hot countries. (It must be borne in mind that though often called "White Ants," they stand in no relation to the true Ants.) Mr Bates, has given us an excellent description of the habits of these singular insects, from which much of what follows has been taken.
Termites are small, soft-bodied insects, which live in large communities, as do the true Ants. They differ, however, from the Ants in the fact that the workers are individuals of no fully-developed sex, whereas amongst the latter they are undeveloped females. Further, the neuters of the Termites are always composed of two distinct classes or "castes" - the workers and the soldiers. Lastly, the Ants undergo a quiescent pupa-stage ; whereas the young Termites, on their emergence from the egg, do not differ from the adult in any respect except in size.
Each species of Termites consists of several distinct orders or castes, which live together, and constitute populous, organised communities. They inhabit structures known as " Termitaria," consisting of mounds or hillocks, some of which are "five feet high, and are formed of particles of earth worked into a material as hard as stone." The Termitarium has no external aperture for ingress or egress, as far as can be seen, the entrance being placed at some distance, and connected with the central building by means of covered ways and galleries. Each Termitarium is composed of "a vast number of chambers and irregular intercommunicating galleries, built up with particles of earth or vegetable matter, cemented together with the saliva of the insects." Many of "the very large hillocks are the work of many distinct species, each of which uses materials differently compacted, and keeps to its own portion of the tumulus."
A family of Termites consists of a king and queen, of the workers, and of the soldiers. According to the researches of Lespes, Bates, and Fritz
Fig. 186. - Termites (Termes bellicosus). a King, before the wings are cast off; b Queen, with the abdomen distended with eggs; c Worker; d Soldier.
Muller, the workers and soldiers amongst the Termites are not sterile females, but modified larvae, which belong to both sexes, and are arrested in their development (or, rarely, males and females in which the reproductive organs are rudimentary). Fritz Muller has further discovered that, in addition to the winged males and females which are periodically produced in great numbers, there exists in some, if not in all, of the species a second set of males and females, which are destitute of wings. These complementary males and females never leave the termitary in which they are born; and they may take the place of the winged males and females whenever a community fails to secure a royal couple at the proper period. The royal couple are the parents of the colony, and "are always kept together, closely guarded by a detachment of workers, in a large chamber in the very heart of the hive, surrounded by much stronger walls than the other cells. They are both wingless, and immensely larger than the workers and soldiers. The queen, when in her chamber, is always found in a gravid condition, her abdomen enormously distended with eggs, which, as fast as they come forth, are conveyed, by a relay of workers, in their mouths, from the royal chamber to the minor cells dispersed through the hive."
At the beginning of the rainy season a number of winged males and females are produced, which, when they arrive at maturity, leave the hive, and fly abroad. They then shed their wings (a special provision for this existing in a natural seam running across the root of the wing and dividing the nervures); they pair, and then become the kings and queens of future colonies.
The workers and the soldiers are distinct from the moment of their emergence from the egg, and they do not acquire their special characteristics in consequence of any difference of food or treatment. Both are wingless, and they differ solely in the armature of the head. The duties of the workers are to " build, make covered roads, nurse the young brood from the egg upwards, take care of the king and queen, who are the progenitors of the whole colony, and secure the exit of the males and females when they acquire wings, and fly out to pair and disseminate the race." The duties of the soldiers are to defend the community from all attacks which may be made upon its peace, for which purpose the mandibles are greatly developed.