DRAGON-FLIES. 9 



base, there is a short, thick, transverse nervule called the 'nodus,' which 

 stops the sub-costal nervure. The nervules between the nodus and the base 

 of the wing are called ' ante-nodals ' or ' ante-cubitals,' while those 

 between the nodus and the pterostigma are called ' post-nodals ' or ' post- 

 cubitals.' All the nervines which cross the wing obliquely are called 

 ' sectors.' That which starts from the nodus is the ' nodal sector,' the one 

 next behind it is the ' sub-nodal sector.' Below the sub-costal nervure comes 

 the ' median nervure,' and then the ' sub-median.' The first cross-nervule 

 uniting the median with the sub-median is the ' arculus,' which sends off 

 two sectors. The upper one of these branches, and that branch next to the 

 median nervure is called the ' principal sector,' while the posterior branch 

 forms the 'median sector.' The 'triangle' is an easily recognised area 

 which lies just below the sub-median nervure and a little outside the 

 arculus " (Hutton). 



The dragon-flies are well known to every one, and con- 

 stitute one of the most distinct and easily recognised 

 families of insects, their elegant structure, beautiful 

 colours, and wonderful powers of flight render them of 

 exceptional interest, even to the most casual observer of 

 natural objects. In addition to the special characters 

 above summarised, dragon-flies exhibit many remarkable 

 peculiarities, when compared with other insects. The 

 structure of the thorax is, for instance, quite unique. 

 The prothorax is small, and often partially concealed in 

 the concavity at the back of the head. The meso- and 

 meta-thorax are very intimately combined, and their 

 relations are such, that the former is placed much above 

 the latter. This peculiarity is carried to its greatest 

 extent in some of the Agrionince where, not only are the 

 wings placed at a considerable distance behind the three 

 pairs of legs, but also the fore- wings are placed almost 

 directly above the hind pair. In the Anisopterides these 

 peculiarities are much less marked ; but even in them the 

 three pairs of legs are placed quite in front of the wings. 

 The legs are slender, and are chiefly remarkable for the 

 beautiful series of hair-like spines, with which they are 

 armed. Their position in relation to other parts of the 

 body is peculiar to the dragon-flies ; the legs seem unlit 

 for walking, the insects never using them for that 

 purpose ; but it is probable that they are of great im- 

 portance in capturing the prey. 



Perhaps the most striking anatomical peculiarity of 

 the dragon-flies is to be found in the structure of the 

 male organs of reproduction. The ejaculatory duct opens 

 on the ventral plate of the penultimate segment, but the 

 organs of intromission are, however, placed on the under 

 side of the second segment. The precise mode in which 

 the fertilising fluid is transferred from the ninth to the 



