61 



(3) Median lobe (ligula) usually not projecting, entire, and 



in our only species straight and fringed with hairs. 



(4) Palpi rather simple. 



(5) Moveable hook strong and well developed. 

 The flat surface and somewhat simple palpi are archaic. 



2. Cordulegasterinae. Cordnlei/aster amudatus, Lair. (PI. VIII., 



fig. 2). 



(1) Spoon-shaped. 



(2) Kaptorial setae, both lateral and mental— in oar only 



species four on the palpi, about sixteen on the mentum. 



(3) Median lobe produced, and then cleft at the tip. 



(4) On the distal margin of palpi, large interlocking teeth. 



(5) Moveable hook reduced. 



The cleft median lobe (ligula) is an archaic feature. In some respects 

 this mask approaches the very spoon-shaped mask of the Lihelhdidae : but 

 perhaps it is only a case of parallel development, as the two sub-families do 

 not seem to be related. 



8. Aeschninae. Aeschna (jrandix, Linn. (PI. VIII., fig. 3). 



(1) Shape, very long, narrowed towards the base. 



(2) Setae, not present in full-grown naiads. 



(3) Median lobe usually projecting a little, and sometimes 



having a slight median cleft. 



(4) Palpi with straight distal margin, and slight end hook. 



(5) Moveable hook strongly developed. 



The Brachi/tron group may have two pairs of tubercles on the median 

 lobe, which are perhaps remnants of galeae and laciniae. Ana.v, as a naiad, 

 develops towards simplicity. Eudimenlary setae on the palpi may be seen i» 

 the early stages of the naiad ; but they disappear later. The Aeschninae are 

 a fairly archaic type. 



4. Libellulidae. Libellula quad) imacidata, Linn. (PI. VIII., 



fig. 4). 



(1) Mentiim wide and somewhat triangular, subinentum 



narrow. 



(2) Median lobe projecting and triangular. 



(3) PflZ/)/, very large, sub-triangular, very much spoon-shaped. 



(4) Lateral and mental raptorial setae present, the latter 



being sometimes in two series. 



(5) Moveable hook small and slender. 



(6) Distal border much developed. 



The mask hides the face well, but is not so good a raptorial instrument. 

 It perhaps acts as a spoon to catch small animals. In Orthetnnn cancellatitm, 

 Linn., there is a raised central line, and on each side there are a number of 

 small teeth with a small spinule between them. 



5. Calopterygidae. Caloiiteryx splendens, Harris (PI. VIII., 



fig. 6). 



