NO. 15 ARTHROPOD HOSTS OF HELMINTHS HALL 71 



My friend, Dr. Wm. A. Riley, has called my attention to Stein's 

 pioneer contributions ; conceding the point, Stein's good example has 

 not been followed by most entomologists. The competent worker in 

 either field should be primarily a zoologist, and as such able to see 

 the possibilities for cooperation with other zoologists in connection 

 with incidental findings which come to his attention. The larval 

 helminth in an arthropod is an animal which concerns the helmin- 

 thologist in one direction and the " arthropodologist " in another. A 

 sound consideration of the worm calls for a sound consideration of 

 its host, and vice versa. Prophylactic measures directed against het- 

 eroxenous worms call for control measures for intermediate hosts, and 

 if this host is an arthropod the helminthologist must draw on the 

 knowledge of the man who knows about arthropods. 



One of the promising developments in this connection is the fact 

 that whereas the entomologist in the past has devoted his attention to 

 the outside of the insects with only casual attention to the internal 

 anatomy, there is now a tendency to devote more attention to the 

 internal structures. In examining the interior of the insects, the 

 entomologist is certain to find larval worms in some of them. In such 

 cases he would be rendering a service if he would do one of the fol- 

 lowing things: 



If the entomologist is well trained in zoology, and has the time, 

 facilities, and inclination to carry out an adequate investigation of 

 these worms, he can proceed with feeding experiments and ascertain 

 the life history. Lacking the training, time, facilities, or inclination to 

 to do such work, he can turn the material over to a parasitologist for 

 investigation, or call attention in his publications to his findings in 

 order that they may serve as a guide to the parasitologist who is 

 working along this line. 



Some of the hosts given in this paper are not well established, but 

 are included for completeness. In establishing a life history for a 

 parasitic worm, one may be guided with profit by the remarks of 

 Stiles in 1896 in connection with the life histories of bird tapeworms : 



The known or supposed life history has been based upon four different methods 

 of work, i. e. : 



1. Experimental infection of the fowls by feeding to them known larval stages 

 found in invertebrates, and thus raising the adult stage. 



2. Experimental infection of invertebrates by feeding to them the eggs of 

 tapeworms found in birds, and thus raising the larval stage. 



3. Comparison of the hooks upon the heads of adult tapeworms of birds with 

 the hooks of larvae found in invertebrates, and thus associating the young and 

 the old stages. 



4. Wild speculations as to the intermediate hosts, based upon negative results 

 and totally devoid of any scientific foundation. 



