592 ON THE GENUS DIPHLEBIA, 



[For comparison of male appendages, see Plate xx., figs.2-5. 

 These appendages are very thick and of rough surface, being 

 covered all over with tiny spines and other irregularities; hence 

 they are exceedingly ditRcult to represent by a cainera-lucida 

 drawing. In determining a species, therefore, by means of these 

 appendages, one must be prepared for individuals of the same 

 species showing minor difterences, which may lie due either to the 

 individual itself, or more probably to the particular angle from 

 which the appendages are drawn, the outline of the thick inferipr 

 appendages especially changing rapidly with the angle of vision.] 



To separate the three known females (that of D. hyhriduides 

 being so far undiscovered) is a more ditRcult task. The protho- 

 racic differences seem scarcely sufficient to rely upon, and the 

 same may be said of the structure of the occiput. The male 

 appendages being very similar in plan, we might reasonably infer 

 this to be the case with the occiput and prothorax of the females. 

 The best criteria seem to me to be — ( 1 ) the epicranial pattern; 

 (2) the measurements of the tibia of the fore-leg; (3) the com- 

 parative length and breadth of the wings; (4) the shape of the 

 abdomen. 



(1). The epicranial colouration is a brown pattern on a black 

 ground. This pattern may be divided into two parts - a, the 

 vertical spots, of which there are two, lying between the antenna- 

 base and the basal ocellus on each side of the main lonffitudinal 

 axis; 6, the postocellar or occipital band, lying close to the 

 occipital ridge between the eyes. 



In D. lestdides 5, and D. nympho'ides <^, the vertical spots are 

 very distinct and rounded, but those of D. lestdides have a 

 tendency to a subtriangular shape. In D. euphttdidcs <^, however, 

 the spots are enlarged into elongated, subtriangular patches which 

 are joined by a stalk to the brown edging of the eyes. 



In D. lestdides 9 and D. euphcedides 9 the occipital band is 

 regular, rounded and slightly enlarged at each end, and with a 

 tendency in D. euphcedides 9 to carry a small central spike point, 

 ing forward. In D. nymjjhdides ^ the occipital band is broken 

 and divided into two very irregular, subtriangular patches, 

 notched about the middle forwards (see Plate xix., figs. 9-11). 



