24 NEW ZEALAND NEUROPTEEA. 



the winged insect ; the passage between the two forms is 

 sudden ; the creature in its first winged state is a sub- 

 imago, which by shedding a delicate shin reveals the 

 final form of the individual " (Sharp). 



The following are some of the principal terms employed by systematists. 

 in describing the neuration of these insects : — 



" The anterior margin of the wing is called the 'costal' nervure, and 

 immediately below it is the 'sub-costal'; and below that is the 'radius': 

 none of these are branched. Next comes a nervure which branches very 

 near the base of the wing into an upper, called the ' sector,' and a lower, 

 called the ' prebrachial ' ; further on the sector sends out a second lower 

 branch, the 'cubitus,' which thus lies between the sector and the pre- 

 brachial. Starting again from the base, three longitudinal nervures 

 branch off together, the upper of which is called the ' pobrachial,' the 

 middle the 'anal,' and the lower the 'axillary' nervure" (Hutton). 



The Ephemeridce is one of the most interesting- 

 families of the Neuroptera whether we regard it from 

 the standpoint of the entomologist, the angler, or the 

 general observer of nature. In a purely popular sense 

 the May-flies are probably best known as the types of brief 

 and ineffective life, the name Ephemera being derived 

 from the Greek E^ri/uepog — diurnal — and having allusion 

 to the extremely short space of time which they occupy 

 as perfect insects. If, however, the duration of the 

 preparatory stages of the May-fly is taken into account 

 the total life of the individual is really quite as long as 

 that of most other insects. 



The earlier stages of the May-flies are of great interest 

 and importance ; but the perfect insects shrivel so much 

 in the process of drying that the study of the structure 

 of preserved specimens is not altogether satisfactory. 

 The discrimination between many of the species of 

 May-flies, when in their final condition, is attended 

 with much difficulty to any one but a specialist in the 

 group, whilst in most cases the same insects, in their 

 earlier stages, could be readily distinguished even by an 

 amateur naturalist. 



It is probable that May-fly larvae are more modified for 

 an aquatic life than any other insects. They poassess 

 complex series of tracheal gills, which differ very much 

 in structure amongst the various species (see Plate XL, 

 figs. 14-18). The internal anatomy of the larvae also 

 shows some points of extreme interest. The long tails 

 of the insect serve as auxiliary organs of respiration, and 

 there is a special modification of the great dorsal vessel, 

 by means of which the blood is forced into these appen- 

 dages for respiratory purposes. Owing to the almost. 



