314 journal of economic entomology [vol. 10 



Thysanoptera 

 The only notable injury to cotton in the United States by insects 

 of the order Thysanoptera is that by a western species, the bean 

 thrips {Heliothrips fasciatus) in the Imperial Valley (7 and 20). This 

 species occurs in the Salt River and Yuma Valleys and has been 

 noted as injuring beans in the former section but so far has not been 

 found on cotton in Arizona in injurious numbers. However, temporary 

 injury to a few young cotton plants by another species {Microthrips 

 piercei) was once noted in the Salt River Valley (14). 



ACARINA 



Two species of mites occur in Arizona which are of interest in a 

 consideration of cotton pests. The common two-spotted mite 

 (Tetranychus bimaculatus) is a pest of violets and sometimes of straw- 

 berries in the Salt River Valley but there is no record of its occurrence 

 on cotton anj'where in the arid Southwest. From the fact that hot 

 dry weather is favorable for this pest in the East we must regard it as 

 dangerous in its possibilities as a pest of cotton. The second represen- 

 tative of the Acarina referred to above is the wild cotton blister mite 

 {Eriophyes thurherice Bks.) which is quite destructive to the Thurberia 

 plant and would be an undesirable addition to our list of pests of 

 cultivated cotton if it were to spread from its present habitat. This, 

 so far as known, is limited to certain mountain canyons in southern 

 Arizona. 



In a general consideration of cotton pests a more or less arbitrary 

 standard must be set in deciding what species are worthy of mention. 

 As has been stated, it is not the writer's intention to include in this 

 paper a complete hst of insects which have been collected on cotton 

 and which are capable of doing damage. Only those concerning which 

 definite observations have been recorded are mentioned herein. In 

 comparison with the humid cotton belt it is interesting to note that 

 to date the arid Southwest has a list of 20 species of insects which can 

 be definitely recognized as pests of cultivated cotton and in addition 

 two species of insects and one mite which are pests of Thurberia or 

 Arizona wild cotton, making a total of 23. 



East of the ninety-eighth meridian there are at least 42 insect pests 

 and one mite concerning which we have definite records of appreciable 

 injury to cotton. 



The order Lepidoptera leads in both sections, having 18 in the 

 East and eight in the West. The order Hemiptera follows with 11 in 

 the East and six in the West.^ Four representatives of the order 



'Including one which is common in the arid Southwest of this country and which 

 is known as a cotton pest from observations in arid northern Mexico, which in a 

 general way belongs to the same cotton zone. 



