ORTHOPTERA. 167 



numerous cockroaches (Blattidw), together with stick - insects, ephemerids, and 

 dragon-flies, some of which greatly exceed in size any existing form. One of the 

 dragon-flies (Meganeura monyi), was 13 inches in the length of its body, and each 

 of its wings was quite a foot long. 



The Pseudoneuroptera are distinguished from the Neuroptera by the absence 

 of a pupal stage. While agreeing in this respect with the typical Orthoptera, 

 these insects differ by certain characters not generally considered of the first im- 

 portance. Both pairs of wings in this group are thin and membranous, resembling 

 one another in structure, and the hind-wings do not fold up ; whereas in the true 

 Orthoptera the fore-wings are usually thicker and harder than the hind-wings, 

 and the latter are capable of being folded like a fan. 



The first group is that of the dragon-flies (Odonata), the general 

 appearance of which is too well known to need description. All have 

 a large head, the sides of which are covered almost entirely by the two big, glassy- 

 looking, compound eyes, while on its crown are two or three small simple ocelli. 

 Each of the short and bristle-like antennae has a stouter basal portion by which it 

 is inserted on the forehead. The mouth faces downwards, and has a large semi- 

 circular lip (labrum) in front ; the jaws being strong, horny, and well provided 

 with teeth. The maxillae are without palpi, but their narrow and palp-like outer 

 lobe is often regarded as the real palp. Succeeding the jaws behind is the lower 

 lip (labium), which at its free end is usually slightly cleft in the middle, while its 

 palpi take the form of two dilated and often two-jointed lateral lobes ; these lobes 

 sometimes overlapping one another in front to hide the free end of the lip. The 

 thick and cylindrical thorax is followed by a long slender abdomen, which usually 

 carries at the end two leaf -like or pincer-like appendages. When looked at from 

 the side, the two hinder segments of the thorax appear oblique, with the wings set 

 rather far back above, and the legs pushed forward below. The wings are long, 

 transparent, and traversed by a rich network of veins. The legs are often spiny, 

 and their tarsi are always three-jointed. The position of the accessory organs of 

 the male on the under side of the second abdominal ring is a feature distinguishing 

 dragon-flies from other insects. 



The female dragon-fly deposits her eggs in such a position that the larvae, when 

 hatched, find themselves either in their natural element, the water, or very close 

 to it. In some species the female, accompanied by the male, goes under the water 

 to lay her eggs ; others drop them into the water ; while in many species the 

 female makes incisions in some aquatic plant and there deposits her eggs. The 

 larvae are even more fiercely carnivorous than the adult, and are distinguished 

 from all other aquatic larvae by the possession of a peculiar structure fixed under 

 the head, known as the mask. In their mode of respiration dragon-fly larvae are 

 also peculiar, some being provided with external tracheal gills— in the form of 

 three leaflets placed near the tail-end — which serve also to assist in locomo- 

 tion, while others breathe by means of gills of an exceptional character. 

 The latter are situated in the hinder part of the intestine and consist of six 

 longitudinal bands in its walls, crossed by several transverse folds, supplied 

 with numerous fine branches from the tracheal trunks. Water can be sucked 

 in at the opening, guarded by five valves at the hind end of the body, and 



