208 INSECT TRANSFORMATION 



communities of the Woolly Aphid (Schizoneura lanigera) with 

 their white, waxy, cotton-like, protective covering virgin 

 females and their young in various stages of growth all living in 

 the same way ; further societies of the woolly aphid may be 

 found also on the woody roots. The presence of these sucking 

 insects on the branches and roots results in a response of the 

 plant tissues giving rise to swellings, distortions, and abnormal 

 growths. 



Ripe apples are occasionally to be found the skin of which 

 is cracked, deformed and partly peeled off (Plate II B). This 

 condition is due to the presence on the fruits, during the time 

 of growth, of immature capsid plant bugs 1 ; their puncture 

 of the soft, developing tissues for feeding with the accompany- 

 ing injection of saliva causes decay of the adjacent part of 

 the plant. This mode of feeding on apples by capsid bugs 

 in their early stages is a new phase of behaviour on the 

 part of these insects. One of the species (Plesiocoris rugicollis) 

 is known to have used willow-foliage, as the usual source of 

 its food supply, and there is no doubt that in various localities 

 migran of this species are leaving willow to feed on apple, 

 giving thus a remarkable illustration of the tendency often 

 shown by living creatures to change their surroundings, and 

 to adopt new habits of life. 



It is of interest to notice how the larvae of some insects appear 

 to be dependent for their food supply entirely on some one 

 kind of plant, while other larvae are able to feed equally well 

 on a great variety of plants. For example the caterpillars of 

 the Winter and Vapourer moths, mentioned above, as common 

 pests of apple, may be found on the leaves of an extensive 

 series of deciduous trees, showing great power of adaptability 

 to different surroundings as regards food. Other larvae are 

 able to avail themselves of a wide choice of food-plants within 

 the limits of one large order ; for example, some of the small 

 ermine (Hyponomeuta) caterpillars that feed on apple will live 

 and thrive on other rosaceous trees, such as hawthorn, and 

 hawthorn was probably the original rosaceous food-tree of 

 the Woolly Aphid (Schizoneura) in North America, its native 

 country. On the other hand caterpillars of such specialized 



1 J. C. F. Fryer : " Capsid Bugs ". Journ. B. Agri., Vol. XXII., 1916. 

 K. M. Smith: " Damage to Plant Tissue from the Feeding of Capsid Bugs." 

 Ann. Appl. Biol. VII., 1920. 



