1920] 



Patch: Aphids and Coccids 



157 



For the purpose of illustrating such a cycle, which will give 

 a representation of the family in the complex estate which 

 many of its members have attained, we might focus our atten- 

 tion on that common, widespread, and well known aphid, 

 Eriosoma lanigera, with reference to the outline. Chart II. 



I. APHIDID^. 



Forms and Sequence of Generations Typical for Migrating Aphids.* 



apterous, parthenogenetic, viviparous female — hatch- 

 ing from the overwintering egg and living on 

 primary host. 



parthenogenetic, viviparous females — living on pri- 

 mary host. 



parthenogenetic, viviparous females — developing on 

 primary host and migrating to secondary host. 



parthenogenetic, viviparous females — developing on 

 secondary host. 



parthenogenetic, viviparous females — developing on 

 secondary host migrating to primary host. 



males (4) and oviparous (4) females. 



on primary host. 



V. Sexuparse alata; (3) 



VI. Sexuales 

 I. Eggs 



(4) 



(1) The second and third generations, with certain species, may comprise both 



apterous and alate females; or there may be several generations of either 

 the apterous or the alate females. 



(2) There may be two or more generations like IV which are usually counterparts 



of II. 



(3) The fall migrants may resemble III closely or they may differ markedly. 



(4) These appear but once in the annual cycle. 



* The terms applied to the different aphid forms are very numerous. A tab- 

 ulation of these for uniform reference would be interesting and convenient but too 

 detailed to be in keeping with this brief paper. 



The beautifully elaborated relation of this insect to the 

 nature of its environment, and more the way in which it con- 

 trols and selects its environment, results in a life history the 

 events of which are as thrilling as a tale of enchantment. The 

 stem-mother touches the unfolding elm leaf with her wizard 

 beak and the magic castle appears with its ample shelter. Its 



