HEMIPTERA-HETEROPTERA. 7 



may be included here as it is very closely related to the only other 

 member of the genus, a form occurring in Mexico and Panama. 



Scudder also pointed out that the northern part of Maine and 

 the higher elevations of the mountains of New England are boreal 

 in character, a statement which has likewise been well supported 

 by later investigations, but here the evidence of the present study 

 is less telling, partly for reasons already mentioned, though chiefly 

 because of the interesting fact that most of the Hemiptera peculiar 

 to these portions of our region are species common to the New and 

 Old Worlds. Whether these forms are truly boreal when subjected 

 to Nearctic conditions (though most of them are not so in Europe) ; 

 whether they have been for other reasons unable to spread south- 

 ward; whether they migrated hither from the east or from the 

 west — these are questions which it is impossible to answer now, 

 but which may find explanation when more is known of the dis- 

 tribution of the Hemiptera in Canada. The following are examples 

 of this class, being confined, in New England at least, to northern 

 latitudes or high altitudes: Sciocoris microphthalmus, Nabis lim- 

 hatus, N. flavomarginatus, Didyonota tricornis, Lygus pratensis 

 ruhidus, Mecomma ambulans, Callicorixa praeusta. 



The remaining and larger portion of our region belongs to the 

 Transition Zone in which typically northern and typically southern 

 forms find respectively their southern and northern limits. Here 

 each species is a law unto itself, some extending far into the zone, 

 others for but a short distance. The following may be cited as 

 exhibiting this irregular dispersal: from the south, Piesma cinerea, 

 Leptostyla heidemanni, Hesperotingis antcnnata, SysteUoderes 

 biceps, Phymata crosa, Zelus socius, Rhynocoris ventralis, Gerris 

 canalicidatus; from the north, Homaemus aeneifrons, Eurygaster 

 alternata, Corizus crassicornis, Ligyrocoris contractus, Calocoris 

 nonegicus, Poeciloscytus unifasciatus, Limnoporus rufoscutellatus. 



Species Common to New England and the Palaeabctic Region. 



More of the species of Hemiptera common to the Nearctic and 

 Palaearctic faunas are to be found in New England, according 



