224 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



In addition to these exterior symptoms it is noticed that the prolegs 

 do not seem to attach themselves easily to objects. In the chrysalis the 

 abdomen is very much swollen and the rings stretched, while in the 

 moth, part of the body and the wings Lave a leaden color. This must 

 not be confounded with a certain natural brownness which some healthy 

 moths exhibit and which extends over the whole body. 



Tests for tJie Determination of Febrine. — The cori)uscles mentioued In 

 the above quotation are found in all the stages of the insect's life from 

 the egg to the moth, whence they again pass from the mother into tiki 

 egg. The disease is, therefore, strictly speaking, more hereditary than 

 is ilaccidity, which passes from one generation to another only in an indi- 

 rect manner, as alreadj^ described. It has been found that corpuscles 

 in the male cannot affect the eggs, and that the disease passes from the 

 female only. Pasteur took advantage of these points in his system of 

 microscopic selection. By making an examination of the female moth 

 he was enabled to predict that if she were pebrinous her issue would 

 also be affected with the malady, while if she were healthy the eggs 

 also would be free from its germ. He found, if the pebrine were con- 

 tracted after the fourth molt, that, under ordinary circumstances, the 

 larva would show no external signs of it, while the moth, and there- 

 fore her issue, would be found to be swarming with cori^uscles. It is 

 wise, if the stock is to be used for reproduction, to microscopically ex- 

 amine some of the worms which spin last, in search of the parasite. 

 If any of the school are diseased, these laggards will most certainly be. 

 Unless the insects, therefore, be submitted to examination at this time 

 or while in the chrysalis state, the silk-raiser may have no means cf 

 ascertaining whether or not the iiebrine exists until the contents of the 

 moth are placed under the microscope, when it will be too late to stifle 

 the cocoons. There is none of the languor in p6brinous worms which 

 is found in the flaccid larvte just before si'unning. The sericulturist 

 therefore, who wishes to obtain good stock, will, if wise, make the ex- 

 amination of the larva and afterwards follow up the jirocess through 

 the different operations to be hereinafter described. 



Isolation and Examination of the Moths. — If left to themselves the 

 insects remain in the chrysalis state for from two to three weeks in our 

 ordinary summer weather. This development may, however, be has- 

 tened or retarded by increasing or lowering the temperature. This 

 fact is taken advantage of to obtain a few adult insects, which may be 

 microscopically examined before the whole lot becomes fully developed. 



We were very much pleased with Maillot's method, which he explained 

 and exhibited to us at Montpellier, in 1884, and here give a description 

 of it in his own words : " Three or four days before the cocoons are taken 

 from the branches, we take, here and there, from the early spinners as 

 well as from the late, several hundred cocoons; as, for example, five 

 hundred from a lot of 90 pounds. This sample should be placed in an 

 oven or warm room, where it will be kept day and night at a tempera- 

 ture of from 100° to 110° E., and a high degree of humidity. In this 

 way the formation of the moths is hastened. As during this time the 

 cocoons of the lot itself are remaining at a temperature of from 75° to 

 00°, and often during the night at even lower temperatures, Ave shall 

 still have time to stifle them if the lot is discarded, or to string them 

 into chains if on the contrary it proves healthy. 



" Every two days we take ten chrysalides from the sample and exam- 

 ine them microscopically for corpuscles. If we find them in the first 

 eight or ten days, no matter in how small quantities, we can be sure 

 that the proportion of p6brinous moths will be considerable. When 



