242 KEPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



of the eggs over winter. Many insects that are douhle-brooded in the south are single- 

 brooded farther north. But I regard the attempt to produce a second brood as the 

 only motive for locust migrations. 



If I am correct, there is nothing easier, as I have frequently suggested, than to pre- 

 dict the course of these migrations and, by means of signal-stations, to advise the 

 farming community, months beforehand, of the direction from which swarms may be 

 expected to come and the time of year when such flights will occur. 



Thanking you for your courtesy in offering me this opportunity of bringing ray views 

 before the public in a permannet form, I remain, 

 Yours, very truly, 



G. M. DODGE. 



Prof. C. V. Riley. 



We concur with all that Mr. Dodge says regarding the migratory 

 movements, but the force of the argument in favor of double-brooded- 

 ness depends on the facts stated regarding the occurrences in 1873. 

 Knowing that the evidence is overwhelmingly in favor of normal single- 

 broodedness, but feeling that the rule did not preclude exceptions, we 

 appealed to Mr. Dodge for reasons lor the confident statement that the 

 young which hatched in June, 1873, were from the eggs laid in May, 

 and not from eggs laid the previous autumn, since hatching, in that lati- 

 tude, from eggs laid the previous fall, is often delayed from one cause 

 and another till into June. Mr. Dodge replied that he did not make the 

 observations himself, not having moved to IS'ebraska till August of that 

 year, but that he was in correspondence at the time with an intelligent 

 person, from whom he obtained the information. We have, therefore, no 

 absolute and positive evidence that the young locusts observed in June 

 were from the eggs laid in May. Supposing, however, that they were, 

 there is still no evidence that the second generation became fledged 

 and flew south in August, because the winged insect which Mr. Dodge 

 found there when he arrived may have come from some other source, 

 since, as will be seen in Chapter II, there was a pretty general invasion 

 from the northwest in the autumn of that year over parts of Colorado, 

 Wyoming, Dakota, l^ebraska, and lowa.^^ 



That a second generation may exceptionally be produced the same 

 season in the Subpermanent region from eggs laid by insects that de- 

 veloped farther south, we have no doubt whatever ; for we found a small 

 proportion of the return insects that were flying over Nebo, Nebr., on 

 the 23d of June, last year, to contain well-developed eggs ; and, aside 

 from Mr. Dodge's conclusions, Mr. Whitman informs us that in a letter 

 received from Mr. W. H. Woods, of O'Brien, O'Brien County, Iowa, the 

 locusts are reported to have come there, in 1873, in comparatively few 

 numbers from the south and southwest. They came June 4, and depos- 

 es An additional fact may be recorded here. In the fall of 1873, after the insects had passed from the 

 north over half of Emmett County, Iowa, Mr. E. B. Soper, of Easterville, ^vrites: 'The -wind changed 

 and blew for six days from the so'ath. The insects refusing to be carried back, kept to the ground and 

 laid many eggs." 



