Sept. 1898.] TOWNSEND & CoCKERFLL : On MEXICAN CoCCID,E. 171 



This species may be considered as taking the place in tropical 

 Mexico of helianthi, which is found in northern Mexico, Texas and 

 New Mexico. While helianthi affects Helianthus, Pluchea, etc., in the 

 temperate region just named, go ssypii affects cotton and other malvaceous 

 plants in the tropical region to the south. Probably the specimens 

 found by Townsend on cotton at Santa Maria, Texas, May 7, 1895, 

 and identified by Tinsley as helianthi var., are nearly or quite the same 

 as the present form. 



P. helianthi and gossypii both differ from yi/ccce, the only other de- 

 scribed Mexican Phenacoccus in lacking the characteristic dark coloring 

 of the antennae and legs. They may be separated from each other by 

 the sac characters already given. 



Massed on stems, stalks and leaves, mostly on underside of latter at 

 base of cultivated ornamental plant called, "amistad," which is very 

 closely allied to cotton and is probably a species of Gossypiiim. Fron- 

 tera, Tabasco, Tune, 1897 (Townsend). Div. Ent., No. 7820. 



Also specimens on twigs, leaves and squares of cotton, Frontera, 

 Tabasco, June, 1897 (Townsend). Div. Ent., No. 78 11. From this 

 material only a single adult 9 was obtained. It agrees in every respect 

 with the specimens from amistad, except that the second and third an- 

 tennal joints are equal in length. Only the first six of the antennal 

 joints are represented in the specimen ; the formula for these would be 

 (23) 1 (456). The sacs are typical. 



Var. a. — Sacs have same general characteristics and appearance, but 

 are uniformly smaller than in typical gossypii. Length of sac, 3 to 5 

 mm.; width 1^ to 2 mm. The legs, including digitules of claw, are 

 same as in gossypii. So also are the other characters of the 9 , except- 

 only those of the antennae, the second and third joints of which are 

 normally quite equal; the approximate antennal formula is 23 (19) 

 (456/8). 



Greatly massed on branches, twigs, stems, and leaves of Mimosa sp., 

 called "sarsa," Las Islas del Rio Usumacinta, some 20 miles or more 

 above Frontera, Tabasco, July 9, 1897 (Townsend). Div. Ent., No. 

 7281. The plants were growing on the edge of the river, and were 

 partially submerged at the time by the high water. 



Subsequently to writing the above, Professor Tinsley has carefully 

 studied these forms of gossypii, and compared them with helianthi. 

 His investigation convinces him that no antennal or other structural 

 character of the adult 9 will serve to differentiate helianthi and gossypii. 

 The easily noticeable differences in external appearance are, however, 

 sufficient to separate them. 



