. NOCTUINA. 183 



certain groups they are quite absent, and in these the eyes 

 are prominent and the head-scales usually not so long or 

 dense. The thorax, in many species, is beautifully decor- 

 ated, the collar in front being raised, broad, and often 

 banded ; the shoulder-lappets frequently uplifted and striped 

 or edged with dark colour, and the middle and back por- 

 tions crowned with crests of erect scales, in large curved 

 tufts, in front and back, often with a dividing hollow or 

 channel down the middle, separating the top and back crests 

 into pairs. In other species these crests exist only at the 

 back, the scales on the front portion being much less erected 

 and smoother, and this crested character is modified gradually 

 and almost imperceptibly through numerous species down to 

 a mere central knob at the back of the thorax formed by the 

 converging tips of rather long scales. In many genera even 

 this is absent. The number of species having crests or tufts 

 of scales on the back of the abdomen is very large, and their 

 variation extreme. In some species the tufts are erect, stiff, 

 and horseshoe-shaped, and occur on from one only, to all 

 the abdominal segments except the last. In others the tufts 

 are broad and blunt, or those on the basal segments are thick 

 and distinct, those on following segments dwindling away 

 and hardly noticeable ; or all are oblique, and more and more 

 oblique, until there is really no tuft at all, or it is quite 

 prostrate and only indicated by its darker colour. In cer- 

 tain groups, on the other hand, the basal tufts are small, and 

 that on the third abdominal segment, or on the third and 

 fifth, tall, slender and graceful, being curved over at the tips. 

 In many species long horizontal tufts or fascicles of pale 

 hair-scales, projecting from the hinder part of the thorax, 

 converge over the basal segments of the abdomen and 

 partially conceal the short abdominal tufts ; while in some 

 species the latter are so fugitive that they are shaken off and 

 lost in specimens which have flown or become in any degree 

 worn, and the species, although really decorated with one or 

 two tufts, becomes credited with none at all — whereby 



