414 NATURAL IIIi^TORY OF HAWAII. 



Of the true wasps,^ the family i" including the social wasps is represented 

 by two or three species, one of which 'i is widely distributed about the islands. 



'I'lic family enil)racing tlie solitary was|)s'- is represented by a lai'ge num- 

 ber of species belonging to the genus OdijiK rax. Eighty-six species were re- 

 ported in the Fauna Hawaiiensis, and a tb)/.en or more species have been added 

 since. Excellent keys to the species occurring on the different islands have 

 been prepared by Dr. Perkins, who reports sixty species from Oahu, eighty- 

 four from ]\lani, Molokai and Lauai. and thirty-two from Kauai. Fourteen 

 species have breii foiuid on 'I'Mutalus. iui'ludiug senile of the rarest, while 

 Kilauea as a locality has yielded twenty-one species. On a single day's col- 

 lecting in lao Valley, Prof. Swezey secured eleven out of sixteen species known 

 to occur in that particular locality, which is about half of those so far rejiorted 

 from the Island of ]\Iaui. 



In this genus tlie abdomen is joined to the thorax by a very short peduncle. 

 The shape of the body and the coloration of the abdomen of many species so 

 closely resemble those of the social wasps, known elsewhere as yellow-jackets, 

 and hornets, that it is quite common to hear these names applied to the con- 

 spicuously-marked species. But as a rule, the Hawaiian Odiiixriis arc nuich 

 more somber in color tluin are species from elsewhere. 



Tile habits of the Hawaiian speries, like those of the genus occurring in 

 other lauils, varies greatly. Some species liurrow into the stems and pithy 

 parts of plants, others into dead wood, while a few liuild single cells of mud, 

 which they attach to leaves of trees. ]\Iany of the species build their nests in 

 the jxirous cavities in tlie lava rock; others nuike their nests in the ground. 



The black I'ock-wasp,'^ one of several species common about vertical ledges 

 of rock, attaches its egg by a slender thread at the back of some small hole in 

 the rock. It then tills the hole with caterpillars that have been paralyzed by its 

 sting. In storing the food for its young it is usually particular to select only 

 the young caterpillar of a single species. ]\lany of these, as we shall see, are 

 leaf-rollers in that they protect themselves from their enemies and the sun in 

 the caterpillar stage by folding the leaf together about them. The wasp, after 

 locating the young caterpillar in its hiding-place, alights on the leaf nearby. 

 The young caterpillar then becomes excited and creeps out of its hiding-place 

 and falls to the ground, whereupon the waiting wasp will pick it >ip, sting it, 

 and carry it away to its storehouse cell. When the cell cavity is full, the 

 ingenious insect plugs up the end of the hole with mud, through wdiich in due 

 time the young wasp M'ill emerge. The habit of storing their cells with the 

 hiiva' of moths and butterflies is very common among the solitary wasps, and 

 as they are active during the year they do much to keep these insects in check. 



The keyhole wasp^-* is a black wasp with dull-blue iridescent wings 

 clouded with brown, that is common about houses, where it employs at least 

 a part of its time in plugging up keyholes. They are interesting and intelli- 



