174 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



vegetation growing upon it were not distributed essentially differ- 

 ently from the above, but' were near to water in the more arid climates. 

 The native pests of our fruit-bearing shrubs and trees were originally 

 less widely distributed than the others because the thickets which sup- 

 ported them were less widely distributed, being confined m.ore generally 

 to the deciduous forest area (Fig. 10) and the savanna or moist 

 prairie area. 



IV. Center of Abundance of Native Pest Species. — We cannot 

 too strongly emphasize the unbroken character of the original forest of 

 the area shown as forested in the map (Fig. 10). Accordingly the pest 

 species referred to above were crowded into the cracks of the forest and 

 scattered along the river margins of the great plains. The area shown 

 as prairie in figure 10 is made up of moist grass land, river skirting 

 forest with groves away from the rivers making the forest edge or 

 thicket of hawthorn and plum a very important habitat in this region. 

 With the extensive moist grass land areas mixed with this, the space 

 available for pest species was great. We may consider the original 

 center of distribution and abundance of native pests as lying" within 

 the area of prairie" or savanna shown in figure 10. 



V. The Expansion of Local Range of Pest Species under 

 Agricultural Conditions. — With the clearing of the land and the 

 putting out of crops in the forest area, the habitats of the pests in the 

 cracks and corners in the forest was expanded to cover the agricultural 

 lands as far as they were cleared. With the building of roads the road- 

 side ditch, roadside thicket and the road itself made a complex support- 

 ing all of the various types we have mentioned (Fig. 3). Thus the 

 local species of primeval conditions took on a general distribution 

 under agricultural conditions. 



Explanation of Plate 7 



1. A pond margin; a type of situation of very wide distribution in North America — • 

 one-third of the phytophagus insects taken here are mentioned by Forbes and Sander- 

 son. 



2. Dry clay bluff supporting such forms as Dissosteira Carolina and the vegetation 

 of which supports the Xiphidiums, aphids^ and plant bugs common on crops grown on 

 high dry ground. 



3. A roadside habitat combining most of those mentioned in the paper as normal 

 to primeval conditions. 



President H. T. Fernald: The next paper on the program will 

 be by Mr. E. G. Titus. He will speak on " A Clean Town Contest. " 



