XVII] 



BIONOMICS, ETC. 



325 



abdomens in slender species occur in the genus Agriocnemis ; in 

 robust species, Nannophya (PL I, fig. 2). 



(ii) Expanse of wing. We may judge of this by measuring 

 the hind-wing. Here again the long slender wings of the Pseudo- 

 stigmatinae are easily first (PI. I, fig. 8). In the robust species 

 the same two genera as above lead the way. For the small species, 

 the rather long-bodied Hemiphlebia vies with Agriocnemis (PL I, 

 fig. 9) in shortness of wing. 



(iii) Robustness. For general robustness of build, but especially 

 for the great thickness and strength of its wing-veins, Petalura 

 stands unrivalled. For excessive slenderness of build, one might 

 single out perhaps Aciagrion, Protoneura and Caconeura as the 

 slenderest amongst a large number of delicate species. 



These results are shewn in the following table : 



Species 

 Mecistogaster lucretia Drury 



Megaloprepus coerulatus 



Drury 

 Petalura ingentissima Till- 



yard 

 Tetracanthagyna vittata 



MacLachlan 

 Tetracanthagyna plagiata 



Waterhouse 



Aciagrion fragilis Tillyard 

 Hemiphlebia mirabilis Selys 

 Agriocnemis hyacinthus 



Tillyard 

 Agriocnemis rubricauda 



Tillyard 



Length of 

 abdomen 



cJ 120-130, 



2 100-110 

 cJ 96-102, 

 2 76-85 



3 92, 2 94 



Length of Breadth of 

 hind-wing abdomen in 

 in mm. middle of body 



Remarks 



^ 59-65, 

 2 59-85 

 <? 56-64. 

 2 70-94 

 <? 71, 2 76 



The longest abdomen 



known 

 The female has the 



longest wing known 

 The most robust 



species known 



80, 2 70 ^ 75, 2 80 



<J 69-76, 

 2 74-75 



cj 19-23 



<J 16-18 



<J 16-17 



c? 73-75, 

 284 



cJ 0-15 mm. The slenderest species 

 10-5-12 

 10-10-5 



<J 9-9-5 



The smallest of all 



Courtship. 



A few interesting observations on this subject are available. 

 In the case of Rhinocypha fenestrella, the mature male has the 

 surface of the tibiae whitened. These it displays to the female, 

 while dancing in the air before her [82]. The male of Calopteryx 

 maculata possesses a shining white ventral spot at the tip of its 

 abdomen, which it displays by curving the abdomen upward 

 and forward, the fore- wings being held motionless, the hind- wings 

 fluttering rapidly [198]. A more prolonged courtship takes place in 



