Jan., 1908.] The Ohio Species of the Genus Disonycha. 423 



THE OHIO SPECIES OF THE GENUS DISONYCHA.* 



Leonard L. Scott. 



The genus Disonycha is a small group of beetles belonging to 

 the family Chrysomelidae. They are generally distributed 

 throughout the United States but are abundant only in certain 

 sections, where they may become of some considerable economic 

 importance. Certain species are distinctly southern in distribu- 

 tion, others are found more commonly in the arid portions of the 

 countr3% while still other species may be found only in sections 

 that are under cultivation. The species seem to possess, to 

 quite a marked degree, the ability to adapt themselves to 

 widely varying environmental conditions and this fact may be 

 responsible for their very general distribution throughout the 

 country. The food plants of the group as a whole are mostly 

 herbaceous although some species may be found feeding on 

 shrubs or even on forest trees. Several species are frequently 

 reported as doing a very considerable amount of injury to the 

 leaves of sugar beets and spinach, the latter becoming so badly 

 eaten as to be unsalable. Lambs-quarter and spiny pigweed are 

 also favorite food plants, but since these plants are not of eco- 

 nomic importance, the injury done to them is beneficial rather 

 than injurious. Two species reported from New York were 

 found quite generally on the common arrow-head, Sagitarria 

 variabilis and also on beets, spinach, Chenapodium album and 

 Amarantus spinosus. 



Some peculiar habits of the group are worth mentioning. In 

 the first place in several of the species upon which observations 

 have been made, the adults and larvae feign death and fall to the 

 ground when suddenly disturbed, although if the approach is 

 made quietly, the adults will either not move or will take wing 

 and fly to another plant. On account of this habit, the cause of 

 the injury to beet-leaves and the like is frequently not observed 

 and may be attributed to other insects. D. quinquevittata has 

 been observed (Ref's. 3, 7) swarming near Yuma, Arizona. 

 About three o'clock in the afternoon an immense swarm, prob- 

 ably 20 or 25 feet thick, was observed passing up the Colorado 

 River, following quite closely the bed of the stream and flying 

 about 50 ft. above the water. When insects migrate, it is usu- 

 ally on account of a lack of food, but since there was an abund- 

 ance of food present in this instance the migration may have 

 been caused by the peculiarly sultry condition of the atmosphere 

 at this time; this is frequently a cause of migration in other 

 groups of insects. Reports of migrations of this species are not 

 known from any other section of the country. 



Although the group has been known for a long time and more 

 or less work of a general nature has been done upon the various 



Pl> * Read at the meeting of the Ohio Academy of Science. 



