458 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXV. 



teridse.) The epistome is usually flat but in two genera of the Zygopte- 

 ridoe, it shows a remarkable development and in them has the appearance 

 of an exaggerated, retrousse nose. The lower border is rounded and the 

 sides are usually prominent and overhanging. The labrum (Plate II, la.) 

 is narrower than the epistome, its sides and lower border being rounded 

 and often notched and its middle grooved by a deep sulcus. The lower lip 

 or " labium ", (Plate II, 1 and Ip.) which differs in the different genera, is 

 composed of three parts, a median, often very minute and triangular or 

 elongate and bifid organ, which is the true labrum, and two lateral which 

 are the labial palps and are composed of two or more segments. The basal 

 segment is small and inconspicuous, the median large and foliate or very 

 narrow according to the species. It, together with the labrum, almost 

 or entirely covers the jaws. The last segment is small and often com- 

 pletely absent in the Libellulinfe. The labium is attached to the under 

 part of the head near the occipital articulation, by a narrow piece known as 

 the "menton.'" 



The maxilke are short and very massive, somewhat molar-shaped, the 

 blunt tooth-like points which they bear, being arranged zig-zag-wise. The 

 maxillary palps are long and formidably armed with long teeth, usually 

 live or six in number and furnished also with long, stoiit bristles which are 

 used to grapple the prey with. In the middle of the mouth and behind 

 the jaws, is seen a membranous organ, the " lingua '", which is covered 

 with imbricated spines. (Libellulines.) Its place in the Agrionines, is 

 taken by the pillars of the fauces or sides of the throat, which also bear 

 similar, imbricated spines. These latter which line practically the whole 

 of the inner lining of the buccal cavity, assist the function of passing the 

 food onward into the tesophagus. 



The Thorax. 



The thorax is formed Of an anterior part known as the " prothorax," 

 (Plate I) and two posterior segments, the meso-and meta-thorax which 

 are fused into one mass, the line of junction being only defined by shallow 

 sutures on the sides. The prothorax presents three lobes, an anterior, 

 the " pronotum," which articulates with the head, a middle and a pos- 

 terior lobe which last is useful for classification on account of its great 

 variability. Tiiis posterior lobe has in the different species, a simple or 

 notched border and it may be bi-or tri-lobed, triangular, obtuse or acute 

 and often bears on its free border, a ruff of long, stiff hairs which interlace 

 with a ring of shorter, stiff ciiite lining the margin of the occipital cavity. 



The thorax proper, is usually robust, quadrilateral but sloping above 

 and in front and beneath and behind, so that viewed from the side it 

 appears somewhat lozenge-shaped. The anterior part of the dorsum 

 slopes rapidly towards the prothorax, its borders, which form the " humeral 

 region," often being the site of broad, coloured fascire. Laterally are 

 seen two sutures, one slightly anterior to the middle line and the other 

 between the meso-and meta-thorax. Between these two sutures, situated 

 rather low down, is seen a small papilhe, on the summit of which opens 

 the " thoracic spiracle." This is the respiratory jjore through which the 

 insect takes in and expires air. On the upper and posterior part of the 

 thorax are attached two pairs of wings, springing from chitinous out- 

 growths and separated by a space, the " tergum," which contains <ither, 

 minute processes which serve for the attachment of the muscles working 

 the wings. 



(Note. — The systems of nomenclature of the wing-parts, adopted by 

 French, British, American and (ierman writers are all different, the 

 French and especially the (<erman being abnormally clumsy. That given 

 here, is a compromise and a simplification of the whole, e.<j., instead of 



