June, '17] MORRILL: SOUTHWESTERN COTTON PESTS 309 



In this paper no attempt is made to name all of the different species 

 of insects which have been found on cotton or in cotton fields. There 

 are dozens of insects, especially among the Hemiptera, which are 

 commonly found on the cotton plant and which are recognized as 

 capable of becoming injurious but which are not known to have done 

 noticeable damage to cotton so far. In the future some of these 

 species will increase injuriously from time to time, usually in restricted 

 localities, while others w^hich have already demonstrated their in- 

 juriousness will from time to time become temporarily of little or no 

 consequence as cotton pests. 



Hemiptera 



Up to the present time the insect order Hemiptera has provided 

 the largest number of the more destructive cotton pests found through 

 the section under consideration and in Arizona and California, at least, 

 these insects promise to become the most troublesome group judged 

 from their combined capacity for damage to cotton. 



In west Texas the conchuela (Chlorochroa ligata) (12 and 13) is 

 the most prominent plant bug having a history as a cotton pest. This 

 insect has been taken at various points in southern Arizona. It was 

 found feeding on the bolls of Thurberia in the Santa Rita Mountains 

 but so far as known has not been taken on cultivated cotton in Arizona 

 or California. It occurs in the Salt River Valley, a single specimen 

 having been taken near Mesa on alfalfa. 



The brown cotton bug (Euschistus servus) of the humid cotton- 

 growing states (13) is represented in Arizona cotton fields by one of 

 the same genus {E. im^nctiventris) which up to this time has proven 

 to be our most common pentatomid cotton pest. This has been of 

 common occurrence on cotton in the Salt River Valley and in the lower 

 Colorado Valley near Yuma but like its eastern relative its injurious- 

 ness is due to its general occurrence in small numbers in almost all 

 cotton fields rather than to fluctuating abundance and occasionally 

 severe outbreaks. 



The Arizona cotton stainer (Dysdercus albidiventris) has been the 

 cause of the most severe local insect injury to cotton so far observed 

 in the Salt River Valley (17). It has also been found on cotton in the 

 Gila Valley near Sacaton but has not been reported from the cotton- 

 growing district of southwestern Arizona and southeastern California. 

 Another Pyrrhocorid bug, Euryopthalmus { = Larg'Us) succinctus, is 

 common and widely distributed in the arid Southwest but there is 

 only one record of its occurring on cotton in sufficient numbers to do 

 noticeable injury. This observation (13) was made in western Texas. 

 In the extreme arid Southwest it has been taken on cotton near Bard, 

 California; Florence, Arizona; and Mesa, Arizona. 



