85 



interest, each one being in a way an unknown problem to be 

 solved ; for, unless each one has been studied independently, its 

 host, habits, etc., cannot be definitely know^i, although they may 

 often be approximately predicted it the habits of those closely 

 related are known. Many insect parasites have been accurately 

 studied, but of the great majority tnere is yet much to be learned. 



Aside from the scientific interest taken in them, their economic 

 importance in keeping insect pests in check has been another 

 reason why so much attention has been given to parasitic in- 

 sects the past few years. Whenever investigations are made of 

 insect pests, one feature of them is the study of parasites, to de- 

 termine if there are any in connection with the pest, and if so, 

 how effective they are. If none are found to be present, investi- 

 gations are made to ascertain whether there may be parasites on 

 the same pest elsewhere which might be secured for use in this 

 particular case. Thus there has been a great deal done in the 

 way of introducing parasites from another country, and even 

 from the opposite side of the world. This has sometimes been 

 accomplished successfully ; but has often resulted in failure. 

 There are, however, many important examples of the success of 

 the project, with some of which you are all no doubt familiar. 



Among the first of these introductions of beneficial insects 

 from other parts of the world, was the introduction to Califor- 

 nia of the Australian ladybird beetle which destroys the cottony 

 cushion scale. This was accomplished by Mr. Albert Koebele in 

 1889, and although ladybirds are not parasites, it is an example 

 of the same class of work. Air. Koebele did introduce a parasite 

 at the same time, however, but it was the ladybird that was suc- 

 cessful and effective against the scale insect. 



A familiar instance of successful introduction of parasites is 

 the introduction of egg-parasites for the sugar cane leaf-hopper 

 in Hawaii. These parasites were introduced from Australia in 

 1904 by Dr. Perkins and Mr. Koebele. The results are too well 

 known to need rehearsing at this time. 



A striking example of unsuccessful attempts to introduce ef- 

 fective parasites, is that of Mr. Geo. Compere, who for several 

 years sought many parts of the world for parasites of the Mediter- 

 ranean fruitfly, to introduce into Western Australia. He finally 

 secured several species of parasites in India, which were suc- 

 cessfully introduced into Western Australia, and at first were 

 reported as very satisfactory. More recent reports, however, are 

 that the parasites have not proved effective. 



Many more examples could be given of successful introduc- 

 tion of parasites, and unsuccessful attempts as well. Economic 

 entomologists the world over are becoming more and more in- 

 terested in this aspect of insect parasitism ; and numerous are the 

 experiments now going on in the attempt to find and introduce 

 parasites from one part of the world to another to assist in the 

 warfare against insect pests. There is hardly time to treat of all 



