110 THE CANADIAN ENTOMOLOGIST. 



Atlantic region. Here we have a form undeniably Palsearctic in 

 origin, which has migrated from its native source and travelled 

 15,000 miles to found its colonies throughout the North Tem- 

 perate Zone. Its route has certainly been via Bering Straits into 

 Alaska and thence east and south. Its habitat and its predaceous 

 nature have both contributed largely to its fitness for this long 

 voyage. It is furnished with good wings, sucks any insect it can 

 overcome and lives on the surface of the water. It has there- 

 fore had an unimpeded and favourable route from the land of its 

 nativity eastw^ard until stopped at the impassable barrier of the 

 Atlantic ocean. Thus also must have migrated the two Corixas^ 

 gerniari and prceusta, out from the Palfearctic region. 



This also is the route followed by many of the land bugs, 

 but they indeed must have met the great obstacles, saving only 

 the semi-aquatic strong-flying and predaceous Acanthiida?, to 

 whom the waters can have no terrors. A number of these 

 terrestrial forms are cannibals and live on other insects, their only 

 requirement being that their prey be not encased in impenetrable 

 armor or too large to be overcome. Zicrona ccerulea may serve 

 as an example of these carnivores, and here we see how much 

 slower has been its progress than that of the aquatic forms, and 

 seemingly it has met with an unsurmountable boundary in the 

 Rocky Mountains. The advent of the phytophagous forms is 

 similarly explained for the majority of cases, in view of the 

 adaptability of the Hemiptera to any vegetable food other than 

 their native food plants, especially when pressed by hunger. The 

 dispersal of one land group, how^ever, is a subject for interesting 

 speculation. I refer to the three species of Aradids common to 

 the Eastern United States aud Western Europe. Is this their 

 native home? The genus Aradus is boreal in its origin. This 

 much is reasonably certain. But are these three species them- 

 selves of Pala?arctic or Nearctic origin? And if of Palaarctic 

 origin, how did they get there? And if not, how did they cross 

 Europe? 



Aradus crenatus was described by Say in 1832; subsequently 

 Herrich-Schaefer described it and figured it in Wanzenartigen 

 Insekten (IX., fig. 538, p. 90), under the misnomer corticalis; and 

 in 1860 Leon Dufour described it as new, and called it dilatatus. 



