ECONOMIC ZOOLOGY ENTOMOLOGY. 57 



T. thcspcsioide.s, a i)l;iiit so nearly like cotton that the Mexicans and natives 

 call It wild cotton. 



A close examination of this weevil has disclosed many minor points of dif- 

 ference from the usual form of the cotton boll weevil {Anihonomua grandis). 

 The Arizona form may be found in hibernation in cells until September 1, 

 while the eastern form is never found in cells in cotton bolls after March 15. 

 On Thurberia the Arizona form seems to be confined to one or not more than 

 two annual generations and is found at an altitude of 4,000 ft. and higher, while 

 the cotton boll weevil has many generations and has never been found above 

 an altitude of 2,000 ft. Experiments have shown that the cotton boll weevil 

 will readily and eagerly feed upon Thurberia squares and bolls and that the 

 Thurberia- weevil will feed upon and develop in cotton squares. It is stated 

 that B. R. Coad has succeeded in rearing undoubted crosses between the two 

 varieties from females of each form, although these hybrid offspring were 

 somewhat undersized. 



The evidence presented has led the author to conclude that the two forms 

 represent merely two subspecies, or varieties, or geographic races of a single 

 species, and he here describes the Arizona form as a new variety under the 

 name A. grandis thurheriw. 



It is not known whether the Thurberia weevil hibernates as an adult out- 

 side of its cell, but it has been found that many individuals pass the winter and 

 even the summer in the cells formed during the preceding fall. The natural 

 dormant period of the Arizona weevil lasts about 9 months. Thurberia weevils 

 extracted from their cells in May and sent to Victoria, Tex., immediately began 

 to feed and develop upon cotton and produced several generations. Thus the 

 Thurberia weevil has either acquired by long years of adversity an ability 

 to survive for a longer period without food, assuming A. grandis to be the origi- 

 nal species, or, if the Thurberia weevil is the true original form, then the 

 ability to obtain a plentiful supply of early food has caused the species to lose 

 some of its resistance to adversity. The development of the Thurberia weevil 

 on its native host has not been studied, but it has been observed at Victoria 

 on cotton and the period required for its development found to be practically 

 the same as for the cotton boll weevil. Thurberia weevils removed from hiber- 

 nation in June and transplanted on cotton began reproducing at once and con- 

 tinued to do so throughout the season. 



The host plant of this new form grows at altitudes of from 2,250 to 7,000 ft. 

 and is found at the bottom of the canyons, on the canyon walls, and on the 

 top of the ridges, growing usually where protected more or less from the 

 greatest heat of the sun. It begins flowering in some localities in July, while 

 in others it is just beginning to bud in the latter part of August. The flower- 

 ing continues into October. The plants are perennial, growing to over 10 ft. 

 in height with a spread of about 10 ft. 



At least two species of parasites, a species of Cerambycobius and an un- 

 determined braconid, attack the Thurberia weevil in the Santa Rita Mountains. 



This new weevil becomes of economic importance in that cotton is now being 

 cultivated under irrigation in several localities in Arizona and in the Imperial 

 and Colorado River valleys in California. Thurberia is said to occur in nejirly 

 every mountain range in southwestern Arizona where there is any moisture. 

 In the vicinity of the Santa Cruz Valley cotton is grown within 5 miles of 

 Thurberia plants, and the weevil was found abundant within not more than 

 10 miles from such cotton. Thurberia is also known to occur in Fish Creek 

 Canyon, one of the sources of the Salt River, in which valley the most exten- 

 sive cotton plantings in Arizona are found, and in the mountains to the nortti 

 and south of the Gila River Valley. 



