August, ’24] 
HAMLIN: PRICKLY-PEAR CONTROL 
457 
prickly-pear. They did not inhabit the terminal joints and the pear 
exhibited little external evidence of their presence. Some 6 to 8 larvae 
inhabited the same cavity. The writer is of the opinion that this is 
probably a distinct species, related to the preceding one taken at 
Tlalpam. 
Near Cuernavaca, Mr. E. Mortensen collected a single adult of 
Cactophagus spinolae on prickly-pear. Larval injury, presumably by 
larvae of this weevil, was also noted by Mr. Mortensen at Guajamalpa, 
D. F. on November 19. On the same date between San Angel and 
Coyoacan Mr. Mortensen and the writer discovered larvae, undoubtedly 
of this weevil, tunnelling in heavy middle joints of prickly-pear. 
On November 10 the cactus collection in Chapultepec Park, Mexico 
City was inspected. The writer found a cochineal on Opuntia tomen- 
tosa. 
At Tampico, Tams. Mr. Mortensen discovered lepidopterous larvae 
similar in appearance to Mimorista flavidissimalis Grote but differing 
from that species in habits. 
On November 5 at Santa Catarina near Monterrey, N. L., the writer 
found bluish-gray larvae living internally in an Opuntia of the Imbricatae 
group. 
On the same occasion Mr. Mortensen collected yellow weevil grubs 
in the distal ends of the same cactus. 
In addition to the above insects, many of the species common to the 
Texas cactus country were seen. Moneilema beetles, apparently of 
many species not occurring in the United States, were found in relative 
abundance in practically all regions visited. 
The first four insects mentioned above would undoubtedly prove 
of great assistance in bringing about biological control of prickly-pear 
in Australia. It is noteworthy that all of these occur within easy work¬ 
ing distance of Mexico City, where transportation facilities are best. 
Inspection of the region during summer would probably bring to light 
other species which were not found during this winter survey. 
Cactus-Enemy Complexes 
Each cactus region of North America has a combination of natural 
enemies which tend to hold prickly-pear in subjugation. Most important 
among these natural enemies are the cactus insects, fungi, and bacteria. 
These natural complexes vary greatly in different regions of North 
America. 
The subjugation of cactus in North America is not due to the action 
