THE CYCLE OF LIFE 457 



There is a rather famous Aphis Schlechtendalia chinensis 

 which makes galls on Rhus semi-alata in Japan and 

 China. The galls are used in dyeing and tanning they 

 are rich in tannin, and in former times they served the 

 Japanese women as a tooth-powder for blackening their 

 teeth. Sasaki has almost cleared up its complicated life- 

 history. There is a succession of wingless females, partheno- 

 genetic and viviparous, and after a time winged females 

 appear which lay eggs containing well-advanced embryos. 

 These develop into wingless females again. No males 

 have been found, and we have a glimpse of a possible 

 continuous Parthenopeia. 



Sometimes the life-cycle is long drawn out, as in the case 

 of the seventeen-year cicadas (Tibicina septendecim), well 

 known in the United States, where they are often called 

 ' locusts '. (A small British relative, Cicadetta montana, is 

 sometimes found in the New Forest.) The peculiarity 

 of the Cicada is that it is specially abundant every seven- 

 teenth year in the northern States, or every thirteenth 

 year in the southern States. The eggs are laid on the 

 twigs of trees ; the larvae drop to the ground and cluster 

 on the roots, sucking the sap ; after a prolonged larval 

 period, there is short pupation, and a broad, black insect, 

 with reddish nervures on its wings, emerges. The loud 

 instrumental music or stridulation made by the males is 

 very familiar. 



Tunicates. The majority of Tunicates, belonging to 

 the Ascidian type, are somewhat nondescript marine 

 animals, of sedentary habit, often compared to wine-skins 

 or leather water-bottles. Until their development was 

 made known, no one suspected that their relationships 

 were with backboned animals. The egg develops into a 



