COLEOPTERA. 151 



vated species, and followed the crop easterly. It is 

 interesting to note that a very closely allied beetle, 

 Doryphoj-ajuncta, refuses to feed upon the cultivated 

 potato. 



SCARAB.EID.^. 



This family includes besides the May-beetle, which 

 we have used as a type, the goldsmith beetle, Cotalpa 

 lanigera, Linn., the familiar ^' xo?>Q-h\\g,'" Macrodacty/i/s 

 subspinosus, Fabr., and the ScarabcEus, sacred to the 

 ancient Egyptians. Some of the largest beetles be- 

 long here, as the Dynastes Hercules from South Amer- 

 ica. The male of this species measures about six 

 inches in length, and it has an immense horn extend- 

 ing forward from the prothorax, and another from the 

 head, so that it has a really formidable aspect. Many 

 of the males of the Lamellicorns have stag-like horns, 

 which are greatly reduced in size in the female. 

 Darwin^ has given figures of sev^eral genera showing 

 the difference in the size of these organs in the two 

 sexes. 



LAMPYRID.E. 



Fig. 92, ^, is one of our common fire- flies, Pho furls 

 Pennsylvanlca ; Fig. 92, b, the larva of another species 

 of Photuris. The luminous organs are situated in the 

 abdomen. According to Westwood, the ^gg, larva, 

 and pupa are all luminous, though the light is brightest 

 in the mature insect. There are various views in 

 regard to the cause of phosphorescence, but it seems 

 probable that the light-giving organs have the power 



^ The Desceni of Man, Vol. I., p. 358. 



