810 



ARTHROPODA 



PHYLUM VII 



are elonyate, 



reticulated, with a nodus, pterostigma, 



Order 27. ODONATA Fabricius.i (Dragon-flies). 



te Insects with very mohile head and large eyes, highly specialised orthopteroid 



mouth parte and small, inconspicuous antennae terminating in a hnstle Thorax 



Z y ^eciaUsed; legs Mar, all placed more anteriorly than the ^v^ngs. The u.ngs 



equal or suhequal in size and similar m texture, membranous, finely 



more or less developed triangulär areas, and 



especially characterised hy 



y ^ ^ r the Crossing of the anterior 



hranches of the medial vein 

 hy the radial sector. Abdo- 

 men slender and elongate, 

 consisting of ten segments 

 and a pair of terminal 

 caliper-like processes (cerci) ; 

 females sometimes with a 

 terebra. The earlier stages 

 of life are aquatic ; the 

 mouth of the nymph develops 

 a peculiar structure called 

 the " masJc." 



True Odonata appear 

 first in the Lower Lias, and 

 are present throughout the 

 Mesozoic and Tertiary. 

 Most of the Jurassic types 

 belong to the siiborder 

 Anisozygoptera, which is 

 represented in the modern 

 fauna by but a single 

 species. The more advanced 

 suborders, Zygoptera and 

 Anisoptera, became domi- 

 nant durin g the Tertiary, 



o 



Fia. 1568. 

 Vl'arsophM)ia eximia Hagen. Lithographie Stone (Kimmeridgian) ; 

 Eichstädt, Bavaria. An Upper Jurassic dragon-fly with long, forwardly 

 directed legs. 5/;j (after Handlirsch). 



and comprise at the present day iipwards of 1000 and 1300 species respectively. 



In the Anisozygoptera the wings are subequal and the nodal region resembles that 

 of the next succeeding suborder, but triangles are not formed by the cubitus and 

 cross-veins. Here belong the extinct families Diasatommidae ; Heterophlebiidae ; 

 Tarsophlebiidae (typified by the genus Tarsophlebia Hagen, Fig. 1568); Steno- 

 phlebiidae and Isophlebiidae. 



In the Anisoptera the hind wings are considerably broader than the front pair, 

 the nodal region is generally situated in the middle of the costal margin and the 

 triangle formed by the cubitus and two cross-veins is well developed. A single 

 species belonging to the genus Gomphoides Selys is known from the English Lias, and 

 a number of allied genera, such as Nannogomphus and Mesuropetala Handl. ; 

 Protolindenia and Gymatophlebia (Fig. 1569) Deichmüller; Aeschnidium Westwood, 

 etc., occur in the Upper Jura. In Tertiary strata the families Gomphidae, Aeschnidae 

 aud Libellulidae are represented by about sixty species. As an example of Tertiary 

 Anisoptera luay be mentioned Stenogomphus carletoni Scudder, from the Eocene strata 

 of Roan Mountain, Colorado. 



^ Kirby, W. F., Syiionymic Catalogxie of Neuroptera Odonata, with an appendix of fossil 

 species. London, lS90.—ÄfuttkoiosH, R. A., Catalogne of the Odonata of North America. Bull. 

 Puhlic Museum of Milvvaukee, 1910, vol. i. 



