Female parasitic wasp Catolaccus grandis attacks a boll weevil 

 larva developing under plastic film in a laboratory. The wasp 

 may be able to help control the boll weevil in tropical regions. 



by indigenous farmers. Boll weevils would thereby 

 have had plenty of chances to adapt to the newly do- 

 mesticated and increasingly plentiful crop. 



As I noted earlier, knowing the identity of the 

 boll weevil's ancestral host is of more than aca- 

 demic interest. Botanists have long searched for cot- 

 ton plants that are resistant to the pest. Although 

 some cultivated varieties are attacked to a lesser de- 

 gree than others, none is sufficiently resistant to pro- 

 duce a decent yield without pesticides or some oth- 

 er tactic of weevil control. That makes evolutionary 

 sense; the boll weevil and cotton have apparently had 

 only a short period of association. Cotton has sim- 

 ply not had time to evolve an effective way to re- 

 duce the damage caused by the pest. The affected 

 species of Haiiipea, however, have several successful 

 tactics for avoiding weevil damage. Further research 

 may lead to the discovery of HaDipca?. chemical and 

 genetic resistance mechanisms, which may be trans- 

 ferable to cotton. 



Likewise, knowing the boll weevil's original host 



holds the potential for finding its natural enemies, 

 which might control the pest without chemicals. 

 The long association of the boll weevil and its close 

 relatives with various species of Haiiipea gave para- 

 sites and predators time to target the association. 

 More than fifteen parasites attack weevils hosted by 

 Hainpca. The most promising of them is a parasitic 

 wasp, Catolaccus (grandis [sec photoi^mph at left]. The 

 female C. {^raiidis lays an egg in the cavity occupied 

 by a boll weevil larva, anci the emerging wasp feeds 

 on its weevil host. Although research on C. grandis 

 has been sidelined by the present success of the U.S. 

 eradication program, the wasp may still be an option 

 for boll-weevil control in tropical regions where 

 abundant wild host plants make eradication difficult. 



The natural history of the boll weevil and its host 

 plants illustrates how the loss of tropical biodi- 

 versity has effects far beyond the equatorial latitudes. 

 With the destruction of tropical habitats, not only 

 plant and animal species, but also valuable informa- 

 tion is lost. Many of the insect pests in the U.S. — 

 including the potato beetles, the pepper weevil, and 

 stem borers that feed on rice and corn — likely come 

 from tropical regions, particularly regions in Mexi- 

 co where crops were domesticated. Wild popula- 

 tions of those insect species and their close relatives 

 continue to survive on wild hosts, many of which 

 remain poorly studied or even unknown. If those 

 species are lost, biologists also lose clues to their evo- 

 lutionary history and relations with their host plants 

 and natural enemies. 



Several of the boll weevil's relatives and their host 

 plants have been identified only in secluded, threat- 

 ened habitats in southern Mexico. At one of my re- 

 search sites in the beautiful lake region of Montebel- 

 lo, in the highlands of Chiapas, the habitat of H. nion- 

 tcbcllensis and the only known population of its weevil 

 parasite were destroyed in a 1998 forest fire. The re- 

 gion's growing human population exerts enormous 

 pressure for land; within the next few years any re- 

 maining populations of this Haiiipca species and their 

 weevils will almost surely be gone. Not only will their 

 extinction be a further blow to the planet's biodiver- 

 sity, but it will also irrevocably limit understanding 

 of the boll weevil and reduce our options in dewl- 

 oping ecologically sounci management tools against 

 an important insect pest. □ 



dication program begins; pheromone 

 fested fields, and the insecticide 

 ;ats them. 



2009 USDA projects boll weevil will be 

 eradicated from the U.S. 



ginia becomes the first 

 ite declared weevil-free. 



2006 Ten states have declared the boll weevil eradicated, and the 



pest is declining in the seven remaining cotton-producing states. 



February 2006 N.M UR AI HIS ^^■>R^ 



35 



