224 BOARD OF AGRICULTURE. 



ing the edge of the leaf under their heads as they go- When 

 full grown, they crawl down the plants and go into the 

 ground, where they change to pupae, and finally to perfect 

 beetles, which come out in August and produce a second 

 brood of larvae, which go into the ground for the winter. 



In regard to the effect of dust on any insect, it is very im- 

 portant to know that insects breathe, not through the mouth, 

 as children think they do, but through openings in the sides 

 of the body. If you take a tobacco worm, or a grasshopper, 

 or any large insect, you will notice on each side of most of 

 the rings of the body, a little spot which is frequently of a 

 different color from the surrounding parts, and if these spots 

 are carefully examined, a little hole will be noticed in each. 

 These holes connect with tubes which branch all through the 

 body. These different openings along the body are connected 

 'together inside, so there is a perfect network of air tubes 

 throughout the interior of an insect, somewhat as the veins 

 and arteries run through our bodies, but the blood of an in- 

 sect is not brought round to any special place to be affected 

 by the air ; the air penetrates all through these tubes to ae- 

 rate the blood. Any fine powder applied to many kinds of 

 insects, especially when they or the plants they are on are 

 wet, may stop up these openings and so suffocate the insects. 



If these openings, called breathing-pores, or spiracles, are 

 stopped up, by touching them with a little oil or varnish, for 

 instance, tlie insect soon dies. In killing insects with any 

 liquid, as benzine or chloroform, the application is more ef- 

 fective if made along the sides of the body than upon the 

 head, as is frequently done. Fine powder or dust undoubt- 

 edly acts beneficially quite as often by obstructing the motions 

 of insects ; they become covered with the substance and roll 

 off the plants on to the ground. 



Capt. Danielson. This is a subject comparatively new to 

 us. I see the vast importance of it, and am very glad that I 

 happen to be here. I tliink we have men here who will be 

 able to give us a great deal of light. I have lived longer 

 than most men here, and our crops seem to be hifested, es- 

 pecially our garden crops, with more insects and worms than 



