( Ixxs ) 



clasi)er (I'l. XXXllI. f. 1. 14 ; PI. XXXIV. f. G). In by far the greater number 

 of species the liarpe is shorter than the clasper. A dense patch of scales is 

 fonnd on tlie har]'e of nearly all Protoparce and in many other Aclierontiinae. 



The right and left clasper and harpe are generally the same in outline and 

 structure. However, there are exceptions, asymmetrical development occurring 

 also in these organs, as will be detailed below. 



The external jilate of the clasper is divided by a longitudinal rib-like 

 incrnssation into a narrow dorsal and a large ventral portion. The dorsal jjart 

 is generally concave above the rib. Upon and near the rib there is a peculiar 

 modification of the scaling found in a great number of Sjjhingidae. We 

 consider it an organ of friction, by means of which a sound of some kind is 

 produced. We do not know whether a similar organ occurs anywhere else 

 among Lepidoptera. There are two types of this organ, the one confined to 

 the iipliiiiqiilac asemiuiopliorae, the other to the Sphiiii/iilai' semanophome. 



In the former group of SpJdngidae it is a j)atch of scales lying more or 

 less flat upon the clasper (PI. LVIII. f. 20—32). The patch as well as the 

 scales vary in the different species (respectively genera) in shape and size. 

 The jjatch is as a rule restricted — being, for instance, narrowly halfmoou-shaped 

 in Frotnmbulyx strigilis (PI. LVIII. f. 30), triangular in Protambulyx euri/alus 

 (PI. LVIII. f. 32). But in some cases it is very l&rge^ Amply pterits (PI. LVIII. 

 f. 29). The scales of the patch are rounded and entire, or elongate and dentate 

 (PI. LVIII. f 3.5) ; the middle ones are lialf erect in Poliana hachholxi and 

 micra. A peculiar modification obtains in Polyptychns trisecta and P. ortho- 

 graphiis (pp. 243. 244). Here the scales are obliterated for the greater part, 

 the dorsal area of the clasper being naked and rough with some granules. 



The friction-organ of the Spliingidae semanopJwrae consists of lanceolate 

 scales which are half erect. The scales are very numerous and small 

 (PI. LVIII. f. 3()), or are reduced in number and have increased in size 

 (PI. LVIII. f 37), the smallest number, namely one, being found in Ilippotion 

 rebeli and isis. The scales are strongly striped, have generally a prominent 

 midrib, and are more or less obviously asymmetrical (PI. LVIII. f. 38) ; they 

 are more often truncate than pointed. In Ort/ba hadeni (PI. XLVI. f. 4) 

 the organ is entirely dift'erent, consisting of a large mass of long, wire-like, 

 brittle hairs. 



Among the Ambulicinne with friction-patcli on the clasper we find a number 

 of species which jiossess a corresponding organ of scales on the inner side of 

 the eiglitli tergite. Tiiis organ is almost confined to the Ambuliciiiae, being 

 found elsewhere only in some ArlirroidiiHae, not in any Sphingidae semanophoiac. 

 Tlie organ consists of one single row of large scales, or of several rows. The 

 scales are ribbed, and are so closely apjilied to each other, or are even soldered 

 together, that they form a kind of ribbon at the apical and lateral edge of the 

 tergite, the flat ends of the ribbon being directed towards the clasper. This 

 ribbon is either continuous from one side to the other (PI. LIX. f. I), or it is 

 interrupted apically (PI. LVIII. f. 39. 4U ; PI. LIX. f. 2). The scales of the 



