PLANTS INSECTICIDAL PROPERTIES. 5 



aiid dusted or sprayed food thereafter was renewed daily. Thus 

 by starting each set of experiments on the same day of the week, 

 the days (Sundays) on which no records were taken always fell on 

 the fifth, twelfth, and nineteenth days of the tests. Very little disease 

 was noticed, and parasitism was not bad among these larvae. 



Tent eater-pillars. — Tent-caterpillar tents were collected in the 

 fields from wild-cherry trees, and were later handled as already 

 described for the webs of webworms. Dusted or sprayed wild-cherry- 

 tree foliage was placed in the jars daily and counts were made daily 

 as usual. Owing to the prevalence of the "wilt" or polyhedral 

 disease, it was necessary to test these larvae while they were in the 

 earliest instars, because during the last instar they were badly 

 diseased. 



Catalpa caterpillars. — Catalpa caterpillars were collected on 

 catalpa trees, and when transferred to the laboratory were treated 

 as described for the webworms and tent caterpillars. 



Roaches. — These insects were reared in a specially constructed 

 roach box which was very suitable for the purpose. On various dates 

 20 or 25 were put in each of several small screen-wire cages in which 

 they were dusted or fed poisoned foods. 



Grasshoppers. — Grasshoppers in the fourth, fifth, and sixth 

 (adult) instars, caught in the fields, were either fed poisoned bran 

 mash in the cheesecloth cages, already described, or were dusted in 

 the small screen-wire cages. 



Fumigating tests. — The insects to be tested were put in the large 

 battery jars, 8 inches (20.32 centimeters) in diameter by 12 inches 

 (30.48 centimeters) tall, each with a capacity of about 9.8 liters; then 

 a 1-gram cone of powder was placed in each jar; next the powder 

 was ignited; and finally a glass cover, almost airtight, was placed 

 over each jar. 



RESULTS OBTAINED BY THE WRITERS. 



The writers have tested 232 preparations from 54 species of plants 

 (not including tests of which the results have already been pub- 

 lished) against a total number of 28 species of insects. Some of the 

 more important results obtained are recorded in Tables 1 to 8. The 

 plants first discussed" are arranged alphabetically by genera, but 

 under the subheading " Comparative results discussed " this arrange- 

 ment is not maintained, although it is for the remainder of the dis- 

 cussion under the heading " Discussion of the less important results 

 obtained." 



For a more complete account of the species of plants discussed, 

 the reader is referred to the " Catalogue of plants tested for or 

 reported to possess insecticidal properties " and to the " Index of 

 botanical and common names of plants catalogued." 



DISCUSSION OF THE MORE IMPORTANT RESULTS OBTAINED. 



AMIANTHIUM OR CROW POISON. 



The writers obtained the following results by using amianthium 

 or crow poison (Chrosperma muscaetoxicum) . The powdered bulbs 



