Odonata 201 



strong cross-nervule. The hind-body is relatively 

 longer than in any other insects; there are ten evident 

 segments, the hindmost carrying a pair of stiff un- 

 jointed cercopods. The male genital armature is 

 situated on the second abdominal segment — a position 

 unknown in any other insects (Eg. ill). 



Habits and Development. — Dragonflies are in- 

 sects of prey, pursuing and capturing smaller insects 

 on the wing. Their flight is powerful, and some 

 species migrate in swarms. They undergo a marked, 

 though '* incomplete " metamorphosis, the larval and 

 nymphal stages being passed in water. The larvs 

 are somewhat sluggish creatures, with more con- 

 spicuous feelers, simpler legs (adapted for walking), 

 and shorter and broader hind-bodies than are possessed 

 by the perfect insects. The most remarkable feature 

 in these larvae is the modification of the second 

 maxillae to form an insect-catching trap — the "mask"; 

 the sub-mentum is elongate and hinged with the 

 head, the mentum also elongate and hinged to the 

 sub-mentum, so that the whole organ can be folded 

 and concealed beneath the head ; a pair of strong, 

 curved hooks with teeth are jointed to the mentum at 

 its tip. When a small water-animal ventures too 

 near the dragonfly-grub's head, the mask is suddenly 

 shot out and these hooks seize the victim (3, 170). 



Two well-marked families of Dragonflies may be 

 distinguished. 



Libellulidse. — The LibelluUcLe are dragonflies of comparatively 

 robust build : the eyes touch each other in the centre of the head. 

 The hindwings are broader at the base than the forewings, and 

 there are at least five cross nervules between the root of each wing 

 and the node. The larvse and nymphs breathe chiefly by means of 

 the rectum, whose walls are pierced by numerous looped air-tubes 

 covered by membranous folds or papills ; a set of plates surrounding 

 the anus form a valve admitting water into the rectum at the 

 insect's will. During late nymphal life they breathe also through 

 thoracic spiracles, thrusting occasionally the head and fore-body out 



