NO. 2281. A REVISION OF CH ALGID-FLIES— PHILLIPS AND EMERY. 435 



external structure. The saws or ovipositors of every species, except 

 one (agrostidis), are i\lustrsitQd,howeYer, so that, whenever necessary, 

 they may be used as a last resort, for identifying a species. There 

 are so few specimens of agrostidis that it seemed inadvisable to 

 mutilate any of them. No descriptions have been drawn up for the 

 ovipositors, since it seemed utterly useless. There is little difference 

 in the ovipositors of the different species as seen in profile; the main 

 difference is in the dorsal view and consists in size, shape, and ar- 

 rangement of denticles. 



There are two more or less distinct types of ovipositors, as will 

 readily be seen by referring to plates I, II, and III. These two 

 types of ovipositors bear a distinct relation to the type of injury 

 inflicted upon the plant by the insect and are also coordinated with 

 the external structure or sculpturing of the thorax. In other words, 

 one is able to determine definitely, with one exception, whether a 

 species inhabits the center of the stem or whether it is a gall-former, 

 by a glance at the ovipositor or the sculpturing of the thorax of the 

 species in question. All gall-formers, with the exception of caftiva^ 

 have the rugulose praescutum (pi. 42, fig. 1) and ovipositors of the 

 general type illustrated in plate 41, with denticles on the rods, while 

 those that inhabit the center of the stem have the reticulate praescu- 

 tum (pi. 42, fig. 2) and the ovipositors of the general type represented 

 by plate 39, figure 2, without denticles on the rods. The exception. 

 captiva^ is apparently more closel}^ related to the species that inhabit 

 the center of the stem. 



Tables for the identification of both males and females are in- 

 cluded, though the males can not always be identified with certainty. 

 Besides, there are a number of species in which males rarely occur, 

 so that, on the whole, identifying a species from males alone is unsat- 

 isfactory. 



The ovipositors may be mounted most easily from freshly killed 

 specimens, though they may readily be mounted from dried speci- 

 mens also by dropping the abdomen in a hot, concentrated solution 

 of potassium or sodium hydrate for a few minutes. The ovipositors 

 may then be dissected out as in fresh specimens, dehydrated in alco- 

 hol, cleared in carbol-zylol and mounted in Canada balsam. 



Genus HARM O LIT A Motschulsky. 



Isosoma Walkek, Ent. Mag., vol. 1, 1832, p. 13. (Not Isosoma Billberg, 

 1820, Colooptera). (Type, Ichneumon verticiUaia Fabricius.) 



Earmolita Motschulsky, Bull. soc. nat. Moscow, vol. 35, 1863, p. 58. 

 (Type, H. Jongicornis IMotscluilsky.) 



Philachyra (Haliday) Walkek, Notes on Chalcid., pt. 1, 1871, p. 7. 



The writers have restricted the genus Earmolita to those species 

 without a carinate occiput and having the praescutum either 

 smoothly reticulate and shining (as in grandis), reticulately lineolate 



