INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 941 



paired dorsal muscle ; (2) lateral and dorsoventral muscles of the 

 meso- and metathoras ; {?■) median dorsoventral whicli raise, while 

 the other two sets depress, the wings. Only two muscles are inserted 

 by means of tendons into the wings, the rotation-axes of which lie 

 parallel to the axis of the body. 



The Libellulida3 want the median wing-muscle; each of their 

 chief muscles is provided with one or two very small accessory 

 muscles. Owing to the structure of their wings the muscles are 

 inserted directly at the base of the thickened nervures of the wing, 

 and all have a superior, and some, in addition, an inferior tendon, 

 while the rotation axes of their wings are set at an angle of from 30° 

 to 55° to the longitudinal axis of the insect itself. 



Salivary Glands of the Odonata.* — The salivary glands of the 

 Odonata (Dragon-flies), although denied by entomologists, exist, says 

 Herr Poletaiew, in all the species of the three families of this sub- 

 order of insects. 



In their structure they present the characters common to acinous 

 glands, and consist of lobules, or glandular grains (acini), whose 

 excretory canals unite by degrees into two principal ducts, one for 

 each gland. These lobules, elongated, and of an o-\'al form, are 

 more numerous in the ^schnidaj and Libellulidas than in the 

 Agrionidee. ^schna grandis L., for example, has more than 150 

 of them, whilst Lcstes sponsa Hansen, has only sixty. In tlie two 

 first-named families, moreover, these lobules are closer, and more 

 interlaced by the trachea3. 



The salivary glands are situated in the prothorax, near or over the 

 first thoracic ganglion. Generally they are in front of the latter, and 

 at the same time in front of the anterior depressor of the wing. In 

 some Libellulidaj — the smallest ones — they arc further back, reaching 

 even to the elevator of the anterior wing (e. g. Libcllala scotica Donov.). 

 The whole cluster affects an oval form. Each of the two principal 

 canals, after reaching the interior of the head, enlarges into a sac or 

 bladder, oval or spherical in form, then is continued as a very short 

 tube, and meeting its congener, constitutes a single duct which opens 

 directly into the mouth under the tongue (ligula). 



Mode of Respiration in the Larvae of the Genus Euphoea 

 (Libellulidae).! — Mr. II. A. llagen describes this as follows : — 



On each side of segments 1-8 of the abdomen is a conical 

 branchial apjiendago with unravelled edges ; three strong, equal, 

 cylindrical, caudal, branchial appendages ; the rectal branchiio formed 

 of three simple columns. 



The existence of latei"ul branchial abdominal appendages is known 

 in tlio genus Sialis, but is altogether unique in the Odonata. 

 Kespiration in the larva of Euphijea is thus possible in four different 

 manners: (1) by stigmata, two on the thorax and eight on tlie 

 abdomen ; (2) by lateral branchial ai)pendages well provided with 



• ^CJomptea RtiKhis,' xci. (1880) p. 129. 



t ' Coinptcs Kondiis S(m\ Kntnmol. Bclg.,' iik etinp of 1st May, 1S80. 



VOL. III. 3 n 



