362 POPULAR SCIENCE MONTHLY 



While they habitually accompany injurious insects wherever they 

 are found, it may happen in a restricted region and an isolated 

 plantation that the beneficial forms are absent, and there will be 

 undoubtedly a benefit in introducing them. It often happens that 

 coniferous forests are ravaged by insects without any of their most 

 important enemies, such as Calosoma sycoplianta. Will it not be oppor- 

 tune in such a case to transport a lot of these beetles from the region 

 where they exist and acclimatize them in the devastated forests, where 

 they have not appeared naturally ? 



Then also with sedentary insects, such as the scale insects, which 

 develop often in closely circumscribed localities, it will be possible, when 

 one chances to find a colony particularly invaded by parasites, to cut 

 off certain branches and carry them into other orchards infested by scale 

 insects and less favored from the point of view of the presence of 

 parasites. 



In 1871-72, Le Baron, in the United States, made some experi- 

 ments in the transportation of the small hymenopterous parasite, 

 Aphelinus mytilaspidh, from one locality to another, attaching the 

 branches covered by parasitized scale insects to infested trees which 

 were found in a region where the Chalcidid parasite did not exist. At 

 the end of the year it was stated that the parasite had become domiciled 

 in that locality. 



Johnson has noticed that another parasite very close to the preced- 

 ing, Aphelinus fuscicollis, may be extremely abundant in certain locali- 

 ties invaded by the San Jose scale, and be totally absent, on the con- 

 trary, in others, and he succeeded in propagating this insect by suspend- 

 ing upon a tree, at small distances, small baskets containing twigs 

 covered with parasitized scale insects. 



In France, Decaux was the promoter of the same method, and in 

 1872 had the honor of attracting attention to the question, making 

 experiments in the transportation of parasites from one locality to 

 another. However justifiable such practises may be in certain deter- 

 mined cases, one can not deny that they have not the certainty which 

 they should have in order to be perfectly convincing. In fact, with an 

 indigenous species, it is very difficult to say that it is, at a given 

 moment, really absent from a locality. If it is absent to-day there is 

 a great chance that it will appear to-morrow, coming from a neighbor- 

 ing region. The experimenter will find himself also exposed to possible 

 criticism, not without reason, that he has attributed a result to his own 

 work when nature would have perfectly accomplished the same thing 

 without his intervention. 



A more profound study of parasites and predaceous insects — of their 

 development, their migrations, their geographical distribution — will 

 show us without doubt and in a more precise way, the real value of the 

 consistent method to be used in transporting indigenous parasites, and 



