12 CHE [MM A TUBE STATE OF THE ODONATA. 



transformed into a large erecl pyramidal horn, a character so far as known 

 unique among the earlier stages of Odonata. 



Head large, the breadth about twice the length; facetted eyes small, in 

 the anterior corner of the head, prominent, conical, always rounded on top; 

 the interior triangular prolongations do not meet each other; but they are 

 continued above and below the eye, making on the sides of the head, and 

 more or less behind the eyes, another triangular prolongation, which reaches 

 nearly to the inferior border of the head. The small prominent eyes of the 

 nympha are transformed in the imago into the separated tubercle on the 

 middle of the hind margin of the eyes, and the non-facetted part represents 

 the large eye of the imago. 



Antenna? short, the two basal joints thicker than the seta, inserted in a 

 cylindrical socket ; first joint longer than the second, and more or less en- 

 larged at tip; seta tapering, five-jointed ; its second joint (the fourth of the 

 antenna) shorter than its first, except in M. ttvniolata ; the others of equal 

 length. The vertex very small, slightly convex ; ocelli very slightly indi- 

 cated, or not at all. The part behind the eyes is by far the largest part of 

 the head, separated from the front part by a double curved transverse suture 

 jusi behind the eyes; fiat, rounded on both sides, notched behind, having a 

 tubercle on each hind angle ; in the Asiatic species, on each side of the me- 

 dian longitudinal suture is a tubercle, as in Epitheca ; this is indicated except 

 in M. transversa in the American species. Mask large, the length greater 

 than the breadth, its apical half spoon-shaped; the mask extends between the 

 middle legs, where it is supported on each side by an elevated ridge. The 

 basal part of the mask is triangular, nearly equilateral, its front margin is 

 bent downward, and projects in an obtuse angle; the palpus large, hollowed 

 out. triangular, nearly equilateral; its closely interlocking edge has six or 

 seven teeth, the uppermost being smallest; the movable hook inserted a 

 little back from the teeth, bent, sharp, long, but sometimes reaching only 

 the base of the opposite one. 



Prothorax narrower than the head ; its hind part largest, as wide as the 

 space between the hind tubercles ol the head ; stigma large, uncovered, 

 The dorsal parts of the thorax flat, quadrangular; the wing cases in full- 

 grown nympha? reach the end of the sixth segment, or a little short of it. 



Abdomen large, fiat, about three fifths of the length of the body, ovate ; 

 breadth three fourths of length, roof-shaped : side margin very sharp, taper- 

 ing on segments 7 to 8, and more abruptly on 9 ; segments 2 to 9 of equal 



