24 MIOCENE FAUNA. 



water, in small brooks and springs,, and that the perfect insects 

 nutter about lazily over lakes, rivers, and ponds, so that they 

 may easily be caught and drowned in the water ; but the Libel- 

 lulce have a much more powerful flight, and are fond of fre- 

 quenting woods and coppices, whilst their larvae live in stagnant 

 muddy water. 



The two common Libellulas of CEningen are met with in whole 

 families together in the dragonfly-bed of the upper quarry, where 

 small specimens are found, as well as half-grown and full-grown 

 dragonflies and pupse with wing-sheaths. Some of them have 

 the labium pressed close to the lower surface of the head ; others 

 have it extended as if in the act of seizing a prey (fig. 231). 

 This labium (lower lip) in the larvae of the dragonflies is of 

 very peculiar construction, and can be extended and drawn 

 back like a hand. Gently the creatures glide towards their 

 victim and seize it by the sudden extension of the labium, which 

 is furnished with a pair of strong jaws at its anterior margin. 

 The state of preservation of the larvae renders it probable that 

 they were killed by some sudden catastrophe. Perhaps the 

 water was heated to boiling by volcanic eruptions, or was im- 

 pregnated with gases : either supposition would account for the 

 congregation of masses of larvse of all ages lying together. 

 The rock enclosing these insects is distinguished by its remark- 

 able hardness and brittleness. 



Libellula depressa, Linn., to which the two commonest Mio- 

 cene dragonflies of CEningen are most nearly allied, is now 

 distributed all over Europe. Two species of JEschna also re- 

 semble a European form (&. mixta, Lat.), and one species of 

 Agrion (A. Aglaope, like A. elegans, Lind.) ; whilst two other 

 Agriones (A. Parthenope and Leucosia) represent South- African 

 types (A. fasciatum and longicaudum) . These are large species. 

 A. Parthenope has a dark transverse band on the wing, which 

 was probably black or metallic during life. 



The Ephemeridse (May -flies or day-flies), which are easily re- 

 cognizable by their long caudal bristles, rise in spring and early 

 summer from the Swiss lakes in immense numbers, and not 

 unfrequently make their way into the houses in the evening. 

 They appear to have been rare in Tertiary times ; at least hitherto 



