435 



or at most merely distorting' or curling' the leaves. There are 

 a few species, however, which have the habit of causing char- 

 acteristic galls to grow on leaves and inhabiting the inside of 

 these galls. 



These species are found in a good many regions of 

 the southern hemisphere and of the southern part of the 

 northern hemisphere. The most northerly representative of 

 this type of Trioza is the species arholensis found in southern 

 United States. One species occurs in Mexico, making galls on 

 avocado leaves, two have been recorded from South Aanerica 

 and several from southern Asia, a large number from Aus- 

 tralia, a few from Malay Archipelago and still others from 

 other southern countries. A few of these have been assigned 

 to another genus, Cccidotrioza, and it is possible that when 

 our knowledge is more complete all these gall makers will be 

 referred to such a genus. 



Nearly all of these gall-forming species of Trioza resemble 

 each other in certain wing venational characteristics and in the 

 male genitalia, thus indicating perhaps a generic relationship 

 to each other and distinct from other species of Trioza. The 

 first marginal cell of the forewing is of a peculiar shape, the 

 cubitus forking at about the midpoint or basad of it. The male 

 anal valve in lateral, or profile, view has a straight anterior 

 margin but the posterior margins (the lateral wings) are char- 

 acteristically convex. 



Although the Hawaiian species have undergone changes in 

 the shape and form of the head, armature of the legs and size 

 and shape of the wings, yet a marked homogeneity in the char- 

 acters above referred to shows not only a close inter-relation- 

 ship among these species but also points to a close affinity of 

 these with the gall forming species of Trioza in Malay Archi- 

 pelago and elsewhere. The fact that many of the Hawaiian 

 species are gall forming is further indication of this affinity. 



Most of the Hawaiian species live upon the foliage of 

 Metrosideros polymorpJia Gaud., called by the Hawaiians 

 ''Ohia lehua", and other species of the same genus. One (and 



