188 Bulletin 87 



matter will be considered later in connection with the discussion 

 of remedies. 



The adult cotton square daubers are about a fifth to one-fourth 

 of an inch in length. They are very variable in color. One form, 

 Lygus elius var. hesperus Knight/ is pale brownish green or green- 

 ish brown, the males conspicuously marked with red on the wing 

 •covers and with more or less black on the front third of body, the 

 females being paler and more uniformly colored than the males. 

 The darker form, found on cotton less commonly than the first 

 mentioned, is the true tarnished plant bug, Lygus pratensis var. 

 ■oblineatus Say.^ The general color is yellowish or bronzy brown, 

 with black and grayish or yellowish markings. 



The adults feed inside the bracts of the cotton square, sucking 

 the rich plant juices from the developing parts of the flower bud. 

 The sucking organs are more slender than the finest needle and 

 leave no trace where they penetrate, but the interior of the injured 

 bud quickly decays, the bracts flare and the whole square becomes 

 yellowish in color and drops from the plant within a few days. 

 Shedding of the squares frequently follows irrigation or heavy 

 rainfall. Shedding caused by the square daubers can be distin- 

 guished by the daubs of yellow excrement which the insect leaves 

 •on the inside of the bracts and on the flower bud. This excrement 

 is a liquid which has a varnish like appearance when dry. Squares 

 v^hich show this characteristic daubing, with no other external 

 evidence of injury, are invariably in process of decay. Very small 

 bolls are also subject to attack but the principal damage is 

 to the squares. Cotton growers should learn to recognize the 

 appearance of the squares and bolls destroyed by the daubers in 

 •order to distinguish between the shedding of the forms from natural 

 causes and from the insect attack. 



The cotton square daubers have been found in injurious abund- 

 ance in a cotton field two miles from the nearest alfalfa, but, as a 

 rule, excessive infestations are traceable to surrounding or adjoining 

 alfalfa fields. The adults can not be destroyed by any spray as far 

 as known and their habits of feeding inside the bracts would make 

 the use of any spray impracticable even if an effective one were 

 "known. The problem of controlling the insects in cotton, therefore, 

 centers in preventing their undue spread from neighboring alfalfa 

 fields and in taking advantage of their activity, when disturbed, to 

 drive them out of a cotton field or to concentrate them in such a 

 way as to reduce the damage. 



>Specimens determined by Mr. H. H. Knight of Cornell University. 



