FAUNA HAWAIIENSIS 



(2) Polistes hebraeus. 



Polistes hebraeus, Fab. Mant. Ins. i. p. 292. 

 Polistes macaensis, Fab. Syst. Piez. p. 272. 



Hab. Oahu and Kauai ; on the plains. Olaa, Hawaii (2000 ft.). 



EUMENIDAE. 



This group is represented by a large number of species of the genus Odyneriis, 

 no less than 86 species being known to me. These Odynerus are of great interest and 

 importance, and exhibit a great diversity of structure in the various species, and 

 will no doubt, at some future period, themselves form several distinct genera. In 

 striking contrast to other Hawaiian aculeates (the Mimesidae, Crabronidae, and Neso- 

 pi'osopis) the specific structural characters, (and even the coloration if a few species 

 are excepted), are remarkably constant. These characters are chiefly found in the 

 general sculpture of the insect, the form of the clypeus, the shape of the dorsum 

 of the second segment of the abdomen, but especially in the structure of the ventral 

 plate of this segment. This ventral segment normally consists of three distinct parts, 

 (i) a smaller basal portion, (2) a transverse sulcature traversed by longitudinal costae, 

 (3) a larger apical portion, with a more or less distinct depression. Each of these 

 parts may furnish useful characters ; the basal portion in some species is large and 

 tumid, the costae may be of great length, moderate, or entirely obsolete, the apical 

 portion may be flattened to the level of the costae or greatly and perpendicularly 

 raised above them, and the depression may be wide, narrow, deep, or obsolete. The 

 habits of the species are of interest. All those that I have been able to observe prey 

 on the larvae of moths (Pyralidae, Noctuidae, and Micro-Lepidoptera), so that the 

 number of caterpillars destroyed must be immense, especially as the wasps appear 

 to be on the wing at all seasons of the year. Their cells are sometimes formed 

 in the ground, often in the wood of dead trees, and in the case of many species in 

 the cavities of the porous blocks of lava. A few build solitary cells of mud, attached to 

 leaves of trees, but these I have only found when the leaf has been rolled up by 

 a spider, the nest of the latter and the cell of the wasp being fixed side by side. 

 That very abundant species O. nigripcnnis is very partial to houses, forming its 

 cells in cavities in woodwork, or unused locks. It also frequently occupies the 

 empty cells of Pelopceiis. 



All the Hawaiian species of the genus belong to the section formerly known 

 as Leionotus. As in the Fossores and Anthophila I have described afresh all the 

 species previously known, whenever I have had specimens for examination, the large 



