Sept. 1898.] Townsend & Cockerell: 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, gossypii 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 yucca , 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 Gossypium. Fron- 
tera, Tabasco, June, 1897 (Townsend). Div. Ent., No. 7820. 
Also specimens on twigs, leaves .and squares of cotton, Frontera, 
Tabasco, June, 1897 (Townsend). Div. Ent., No. 7811. 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 antennce, 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. 
