flower for an indefinite number of years. The flowers collected when just about to 

 expand, dried and powered, are very efficient ss a general insecticide. 



During the past year or two many interesting experiments have been made 

 and valuable results obtained, in the way of artificially introducing disease among com- 

 munities of a caterpillars, sort of caterpillar plague or pestilence, which carries them off by 

 thousands. There is a very fatal disease which appears from time to time among silk 

 worms, the larvaa of Bombyx mori, when bred for the production of silk, a disease which 

 spreads so rapidly that it frequently destroys entire broods of caterpillars within a few 

 days. So destructive has it been, that it is estimated that the silk crop in Europe is 

 injured to the extent of many millions of dollars annually. During the past ten years it is 

 believed to have reduced the income of silk breeders twenty-five per cent, and in 1879, 

 was said to be the main cause of the great falling off in the silk crop of that year, which 

 was only about one-fourth of the amount ordinarily produced. The celebrated Pasteur 

 investigated this disease, and found it to proceed from the presence of an exceedingly 

 minute form of bacteria, so excessively small that it has been estimated that it would 

 require eight millions of them to cover the head of an ordinary pin. When water 

 containing these minute organisms is sprinkled on the leaves on which the silk worms 

 are fed, they are found to be rapidly infected and capable of communicating this 

 pestilential disease to others with which they are associated. The bacteria may be 

 preserved in a torpid condition without loss of effectiveness for at least a year, probably 

 for several years, and that without any particular care, and when required for use can be 

 rapidly propagated in a suitable fluid. 



In my address to you last year I referred to a similar form of disease which had 

 occurred among cut-worms, so abundant in clover fields in the Ottawa district ; and in 

 1878 and 1879 to a similar trouble among the forest tent caterpillers, at that time so 

 abundant. Now, I am glad to be able to report a similar disease ammong the cabbage 

 worms, and to indicate to you some practical results arising from investigations regarding 

 its nature and mode of operation. 



Throughout most of the State of Illinois and in some parts of Michigan, it was 

 observed last autumn, that a large proportion of the cabbage worms sickened and died. 

 Hundreds of their bodies were to be seen rotting on the cabbage leaves, or shrunken and 

 dried to a blackened fragment. This was soon brought under the notice of the State 

 Entomologist of Illinois, Prof. S. A. Forbes, a most careful and indefatigable observer, 

 who at once proceeded to investigate the cause of this caterpillar plague. He found the 

 disease at first to be very unevenly distributed, some isolated fields showing no trace of it, 

 while others not far distant were fairly reeking with death and decay ; but as the season 

 advanced it spread in every direction, until in some districts almost every worm perished. 

 He says, " we can conceive something of the significance of this disease if we imagine the 

 terror and dread which would seize mankind if such a plague should suddenly assail human 

 life. Whole towns would be depopulated, and the dead would rot in the streets by 

 hundreds. There would be no escape for any, because the contagion would be conveyed 

 by the very food and drink by which life was sustained." 



On dissecting specimens of the dead caterpillars the microscope showed their intestines 

 to be full of undigested food, and swarming with a species of micrococcus, which appeared 

 in the form of excessively minute spheres about one twenty-five thousandth of an inch in 

 diameter, sometimes single, sometimes in pairs, and occasionally in strings of from four to 

 eight. He found that these minute organisms could be readily cultivated in beef broth, 

 and that a single drop of fluid from a diseased worm introduced into a vessel of such broth 

 would in two or three days render the whole contents milky with myriads upon myriads 

 of these microscopic organisms, precisely the same as those taken from the diseased larva. 

 He also found by experiment that the disease could be communicated to other species of 

 caterpillars. Experiments continued during the present year have shown that by 

 propagating this form of bacteria in the manner described, and mixing a pint of a well 

 charged culture with a barrel of water, and syringing cabbages with this fluid, the disease 

 may be introduced, thus furnishing us with another means of defence against some of 

 these injurious insects. 



A Dew strawberry insect has appeared in our midst, which is deserving of notice. In 



