APPLIED SYSTEMATICS — SCHMITT 329 



With specimens for comparison, a trained entomologist soon located 

 both the beetle and its larval stages in cane roots on Barbados. It 

 further developed that there it had two natural enemies. The only 

 one in evidence at the time was a so-called blackbird which eagerly 

 followed field hands rooting up cane stumps, to eat the grubs turned 

 up, but unable to reach those beneath the ground. The other natural 

 enemy, a tiny, inconspicuous wasp, was discovered by a neat bit of 

 detective work on the part of the entomologists. Attached to one of 

 several Barbados root borers transmitted to the British Museum was 

 observed a tiny white grub. In the manner of its attachment it sug- 

 gested the larval stage of a small wasp common in Barbados, one of 

 the family of solitary wasps known to parasitize beetle larvae but 

 not heretofore the cane borer. The wasp lays her eggs upon the borers 

 after paralyzing them with her sting so that they will serve as food 

 for her own young on hatching. Introduced into Mauritius, this little 

 wasp soon turned the tables on the cane borer. 



One cannot leave the subject of biological controls in the field of 

 agriculture without touching upon one of the most remarkable suc- 

 cesses of all time. This particular one was made possible by the 

 taxonomic studies that preceded, and were undertaken in connection 

 with it. It was the conquest of the prickly pear in Australia by the 

 cactus moth borer, Cactohlastis. 



Cactuses are peculiar to the New World. As horticultural curiosi- 

 ties, and also as hosts of the cochineal insect, they were introduced 

 shortly after their discovery into many other lands. The dates of 

 the early introductions of the prickly pears, or Opuntias, into Austra- 

 lia are not known. Some planted as hedges and in gardens escaped 

 to run wild in the surrounding country. As with the cane borer in 

 Mauritius, in a favorable environment and without natural enemies 

 to keep them in check, they spread at a tremendous rate. The rapidity 

 of their increase has been called one of the botanical wonders of the 

 world. In a period of 20 years the land area preempted by these 

 prickly pears increased from 10 million to 50 million acres. 



It was imperative that something drastic be done if the Opuntias 

 were not to take over the land. Millions of acres had become veri- 

 table wildernesses of prickly pears. The Australians soon discovered 

 that the cost of eradicating cacti by hand, poison, or mechanical means 

 so greatly exceeded the value of the land that it was prohibitive. 

 Some less costly method would have to be employed if the land was 

 to be reclaimed. Biological control seemed to offer the greatest hope. 

 Forthwith, the systematic literature of the world was searched for all 

 pertinent information — the kinds, distribution, and habits of the 

 prickly pears, and especially the literature relating to the animals 

 and plants that have been reported to live in or upon them. Austral- 

 ian entomologists searched the world, so to speak, for the known and 



