REVISION MALACOSOMA HUBNER IN NORTH AMERICA 115 



hatch from one egg mass, much less eight, so they were forced to eat 

 oak or starve. They had done very well on oak, and it seems that 

 americanum could be a pest of oaks and other trees, were it not for the 

 fact that the females prefer to lay their eggs on other hosts. 



TYPE. — Apparently destroyed. Dr. S. L. Tuxen of the Universitetets 

 Zoologiske Museum in Copenhagen could not find it in either their 

 collection, or in the Kiel collection (now in their museum) where he 

 says it should be. 



TYPE LOCALITY.— Boreal America. 



DISTRIBUTION. — M. americanum is generally distributed through- 

 out the eastern half of the United States and the southern part of 

 eastern Canada (fig. 2). It meets, but only narrowly overlaps, the 

 distribution of M. calif or nicum pluviale to the north, and that of M. 

 calif or nicum lutescens to the west (fig. 2). 



ECONOMIC IMPORTANCE.— It cannot be considered to be a 

 pest which causes extensive economic losses, since most of its hosts have 

 little value. On hosts such as Primus serotina, the black cherry, whose 

 wood is valued for furniture, it may be of some importance since growth 

 is reduced by heavy defoliation, and control is impractical unless 

 relatively pure stands are involved. Neglected fruit trees are often 

 attacked, but commercial orchards are protected by the normal spray 

 program that is used for more serious pests. It can be regarded as a 

 nuisance throughout most of its range, but the large number of leaflets, 

 pamphlets, circulars, and popular articles, which have been published 

 in the past concerning its life history and control, attest to its status as a 

 first-class public nuisance, especially in years of high populations. 



COMMENTS. — M. americanum is completely isolated under field 

 conditions from both M. californicum lutescens and M. californicum 

 pluviale, two subspecies which overlap its distribution to the west and 

 north respectively (fig. 2). No field-collected specimens have been seen 

 which could be interpreted as intermediates between them. The area 

 of overlap between them is not very wide at the present time, and a 

 change from one species to the other may take place in a very narrow 

 zone. In 1962 such an abrupt change was recorded while driving east 

 from the Texas line on Oklahoma 33. Colonies of californicum lutescens 

 were numerous on wild plum, and were occasionally found on Ribes sp. 

 and Prunus virginiana growing along fence rows and gullies. Between 

 Miami, Texas, and 5 miles NE. of Guthrie, Oklahoma (approximately 

 25 miles north of Oklahoma City), 25 stops were made, and more than 

 200 tents were examined. All of them contained only larvae of c. 

 lutescens. Six miles NE. of Guthrie the first colony of americanum was 

 found along with five colonies of c. lutescens. Table 3 shows what was 

 found between Guthrie and Perkins, 26 miles NE. of Guthrie. 



