lower ])arl of the head lu^xl t(i llic tli»»i-ax and ])asscs l)ack 

 pressed aiiaiiist the veiiti-al surface of {\\o thorax hetwecn the 

 front i)air of k'gs and then l)ends (hiwnward. Jn this way a 

 greater leverai>e hy more of the hody is hronght to hear njxni 

 the heak in fcn-eing it into ]dant tissues. 



The iuniiatnre, or nyni])hal, stages of these insects are 

 passed n])on the same jdants with the adnlts, and in tlie same 

 active, sap-sticking manner detrimental to the plant, lu many 

 species the reaction of the insects' activities on the leaves or 

 stems of the jilant and the poison wastes secreted hy the insects 

 canse the growth of tnmors or excrescences of characteristic 

 forms, known as galls. The galls are usually characteristic 

 of certain species and may often he used as an index of the 

 species even though the insects themselves may not he discov- 

 ered. 



The feeding hahits of jumping plant lice render them harm- 

 ful to i)lant life, hut fortunately these tiny insects do not at- 

 tack many of our cultivated or garden plants and therefore 

 thev are considered of relatively small economic importance 

 in agriculture. Moreover, they are far less prolific than are 

 the true plant lice and scale hugs, and f(n- this reason also are 

 viewed with much less concern hy economic entomologists. 



There are a few species of the family which cause consid- 

 erable damage in the orchard, field or garden. The pear 

 psylla (several species, one in each of several countries) causes 

 extensive damage to pear and allied ondiard trees and receives 

 much attention and expensive treatment. The tomato psyllid 

 (Faratrioza cocl-ereUi) is responsible for severe injury to 

 tomatoes and peppers and other plants in southwestern Fnited 

 States. The laurel psyllid (Trioza alarris) seriously disfigures 

 bay trees in Northern Europe and now in the Ignited States, 

 causing the leaves to become much rolled, curled u]) and gen- 

 erally distorted. Other species attack alder tr(>es in America 

 and Euro])e, while another is a pest on citrus trees in llie 

 ^lalay Archipelago and India. 



The family is a relatively small and homogeneous group. 



