436 Mr. Charles J. Galum on 



similarity in position and structure of the stridulating 

 organs in certain families, that these families wore there- 

 fore closely related to each other. 



But the case seems to be different when we come to 

 consider genera and other minor groups within the family, 

 and if certain species of a genus, or certain genera of a 

 family agree in possessing stridulating organs, in the same 

 position, and with the same kind of structure, it is safe to 

 infer that such species or such genera, as the case may be, 

 have derived this character from a common source, and 

 are more closely related to each other than to those species 

 or genera which do not offer the same character. 



These remarks may be illustrated by a further reference 

 to the family Undomychid/u. In all the species I have so 

 far examined belonging to the " groupes " Eitmorphites, 

 CorynomaliUs and LycofcrdiUs — the three groups which 

 come first in Chapuis' arrangement of the family — a 

 stridulating area has been found present on the head in 

 both sexes. It appears to be absent in the other " groupes," 

 or if present, to be present in a most rudimentary condi- 

 tion. The first three "groupes" might therefore be asso- 

 ciated in one large group distinguished by the possession 

 of stridulating organs, and such a group would, I think, be 

 admitted as a natural one. 



Stridulating organs occupying the same position on the 

 head, and very similar in all points of structure to those 

 of the Endomychid.v are very generally present in the 

 Hispidie, but it has never been suggested that these two 

 families are in any way closely related to each other. 



In the Hispidm, as in the Endomycliidx, the stridulating 

 organs have as a rule the same characters in both sexes, 

 the only exception so far met with, occurring in the genus 

 Spilispa, Baly. 



In S'pilisiKL impcricdis, Baly, there is no true stridulating 

 organ in the female, whereas in the male the stridulating 

 area on the crown of the head is well-defined, though 

 somewhat exceptional in structure, the series of ridges of 

 which it is formed being slightly arcuate, less closely 

 approximated than usual, and marked with short longi- 

 tudinal furrows (PI. VII, figs. 2 and 2a). The male of 

 this species is further distinguished by the presence of a 

 small triangular flap, thin and semi-membranous, pro- 

 jecting from the front margin of the pronotum (figs. 2 and 

 2&). What part this flap takes in stridulation does not 



