810 



ARTHROPODA 



PHYLUM VII 



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



Elongate Insects with very mobile head and large eyes, highly specialised orthopteroid 

 mouth parts and small, inconspicuous antennae terminating in a bristle. Thorax 

 highly specialised ; legs similar, all placed more anteriorly than the wings. The wings 

 are elongate, equal or suhequal in size and similar in texture, membranous, finely 

 reticulated, with a nodus, pterostigma, more or less developed triangular areas, and 



especially characterised by 

 / the crossing of the anterior 



) branches of the medial vein 



by 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 " mask." 



True Odonata appear 

 first in the Lower Lias, and 

 are present throughout the 

 Mesozoic and Tertiary. 

 Most of the Jurassic types 

 l)elong to the suborder 

 Anisozygoptera, which is 

 represented in the modern 

 fauna by but a single 

 species. The more advanced 



ZTarsopMehia eriinia Hagen. Lithograpliic Stone (Kimiueridsian) ; suborders, Zygoptera and 

 Biclistadt, Bavaria. An Upper .Jurassic dragon-fly witli long, forwardly Anisoptera became domi- 

 directed legs. 5/.^ (after Handlirsch). ' \, ^ . 



nant durmg the Tertiary, 



and comprise at the present day upwards of 1000 and 1300 sj)ecies 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 Avell 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) Deichmiiller ; Aeschnidium Westwood, 

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

 and Libellulidae are represented by about sixty siaecies. As an example of Tertiary 

 Anisoptera may be mentioned Btenogomphus carletuni Scudder, from the Eocene strata 

 of Roan Mountain, Colorado. 



^ Kirby, W. F., Syiiouyniic Catalogue of Neuroiitera Odonata, with an apiiemlix of fossil 

 species. London, l?>^Q.—Muttkoivski, H. aA., Catalogue of the Odonata of North America. Bull. 

 Pulilic Museum of Milwaukee, 1910, vol. i. 



