THE EFFECT OF MAX 553 



salamanders, frogs, lizards, snakes, and even small rodents and opos- 

 sums. 



Parasites of man and his house pests have followed him every- 

 where; the brown rat and the house mouse and all sorts of small 

 vermin such as house flies, the bedbugs, fleas, and lice are well-known 

 examples. An interesting example of unintentional transport by man 

 is furnished by spread of the sand flea, Sarcopsylla penetrans, in 

 Africa. The female of this species bores into the skin of man, especially 

 beneath the toe nails. A native of Brazil, this species was brought 

 to Ambriz in a ship's cargo in 1872; it ranged from there along the 

 coast, and reached the Congo in the same year and Benguella in 

 1875; in 1885 it had established itself on the entire coast from Sierra 

 Leone to Mossamedes, covering 22° of latitude. It extended inland first 

 along the principal caravan routes, spread by the porters. By 1875 

 it ranged up the Congo to the Inkissi Falls; in 1885 it was reported 

 from Stanley Falls; in 1887 it reached the Nyangwe; in 1891 the west 

 bank of Lake Victoria, via Lake Tanganyika; in 1895 Mpwapwa, in 

 1897 Bagamoyo and Pagani, and in 1898 Zanzibar. Thus this animal 

 crossed Africa in about 25 years. 23 



In North America many of our worst insect pests were brought 

 accidentally from Europe. These include the Hessian fly, wheat midge, 

 gipsy moth, brown-tail moth, European corn-borer, elm-leaf beetle, 

 leopard moth, woolly apple aphid, cabbage butterfly, cabbage aphis, 

 clover root borer, asparagus beetle, imported current worms, and 

 many cutworms. 



Accordingly great care is now exercised in the United States to avoid 

 the introduction either of new pests or of apparently harmless animals 

 which, if released from the control of their normal environment and 

 the biotic control of their natural enemies, may be pests. In addition 

 to quarantines maintained at ports of entry, interstate and inter- 

 region quarantines are established. As a result of their experience 

 with introduced insects which became pests the Bureau of Entomology 

 of the U. S. Department of Agriculture years ago set about the dis- 

 covery and importation of important natural enemies of introduced 

 species. This means of biotic control of insect pests was notably 

 successful with the coccinellid beetles, Novius cardinalis, which were 

 imported from Australia to hold the cottony cushion or fluted scale 

 in check, and the same method has yielded beneficial results in numer- 

 ous other instances. Thus man attempts to restore the balance of 

 nature which he himself has destroyed; despite obvious difficulties, 

 this has now become a standard procedure in pest control. 



