212 TENTH ANNUAL REPORT. 



were it certain that the poison would only be applied under 

 the conditions recommended. But the work must so often 

 fall into the hands of ignorant and unskilled laborers, that 

 the element of danger cannot be ignored. The first positive 

 evidence of the danger that I have seen came to me in a letter 

 from a correspondent at Hill, New Hampshire, who reported 

 that he had known a case in which the members of a family 

 had been made ill by eating cabbages which had been treated 

 with Paris green. 



We tried a large number of experiments with pyrethrum 

 or insect powder as a remedy for the cabbage worm. This is 

 one of the most important of the non-poisonous insecticides, 

 killing caterpillars and other insects by merely coming in con- 

 tact with their bodies. It was found to be effective when 

 applied dry by means of a bellows, either undiluted, or thor- 

 oughly mixed with an equal quantity of flour. It also kills 

 the worm when applied as a decoction made by adding one 

 ounce of pyrethrum to one gallon of boiling water. Much 

 less pyrethrum was required for a given area when it was 

 put on in this way, than when it was used as a dry powder. 

 The decoction is to be applied as a spray, either by means of 

 an atomizing bellows, or a pump and spray nozzle. We also 

 found that a one per cent solution of the Eose Leaf insecticide, 

 a tobacco extract made by the Louisville Tobacco Company 

 effectually kills the worms at a small expense. 



The various stages in the life history of this cabbage worm 

 are illustrated in Plate 11. The adult insect is the common 

 white butterfly, the male of which is shown at c, and the 

 female at d of the plate. The latter deposits, singly, or in 

 clusters of two or three each, small yellow eggs upon the 

 cabbage leaves; these soon hatch into little green larvae that 

 feed upon the substance of the foliage. In about two weeks 

 they become full grown, when they generally leave the cab- 

 bage plants, and finding some suitable shelter — beneath a 

 board or under a coping of a fence, — change to chrysalids. 

 They remain in this condition about ten days, when they 

 emerge as butterflies, to lay eggs for another brood of worms. 

 The winter is passed in the chrysalis state. There are several 



