EGGS NOT THICKLY LAID FOR TWO CONSECUTIVE YEARS. 247 



My correspondents in various portions of the State are generally agreed that no mi- 

 gratory locusts remained over the summer. The few who have, reported otherwise 

 mistook native species for the true insect. 



Mr. Riley Aveut south to Dallas, Tex., and west to Manhattan, Kans., 

 late in the autumn, with a view of making especial observations on this 

 IJoint, and failed to find any specimens of the Eocky Mountain locust 

 remaining, though the Eed-legged and Lesser locusts were sufficiently 

 common; the last species quite so in parts of Kansas, and ovipositing. 

 The experience of 1877 corresponds, therefore, with that of 1875, and 

 we may safely conclude that, with scarcely an exception, the insects 

 which hatch in the Temporary region south of the 42d parallel do not 

 remain to lay eggs. So general is the rule, that where the insects are 

 reported as remaining to lay, it may be assumed as highly probable that 

 the Lesser locust has been mistaken for its large congener. The rule 

 holds less true north of the line indicated. 



EXTENSIVE AND THICK EGG-LAYING SELDOM OCCURS TWICE CONSEC- 

 UTIYELY IN THE SAME LOCALITY. 



The history of the Rocky Mountain locust indicates that in the Tem- 

 porary region its eggs are never laid thickly and extensively in the 

 same locality for two consecutive years. Exceptionally, in restricted 

 locations, eggs may thus be laid for two years consecutively, but the 

 second laying is more apt to come to naught, and the issue from it to 

 perish. This rule will hold less true in the Subpermanent re^^ion, and 

 probably will not apply at all to the species in its permanent confines, 

 though even there, wherever eggs are so thickly laid that the resulting 

 insects devour all the vegetation where they are born, these must of 

 necessity migrate to procreate. 



We shall propound this rule and the probable explanation of it very 

 much in the language in which it was first stated by Mr. liiley before 

 the IsTational Agricultural Congress at its Chicago meeting last autumn: 



In mapping out the country in Kansas and Missouri in which eggs 

 had been laid most thickly in 1876, we were struck with the fact that 

 the very counties in which the young insects had been most numerous 

 and disastrous in 1875 wave passed by or avoided, and had no eggs of 

 any consequence laid in them in 1876. The fact was all the more obvi- 

 ous because the insects did much damage to Fall-wheat, and laid eggs 

 all around those counties to the north and south and west. From the 

 exhaustive report on the insect in Minnesota, made by Mr. Allen Whit- 

 man, it was also very obvious that those portions of that State which 

 had been most thickly supplied with eggs in 1875, and most injured by 

 the young insects in 1876, were the freest from eggs laid by the late 

 swarms of the latter year, notwithstanding counties all around them 

 were thickly supplied. We were at first inclined to look upon these 

 facts as singular coincidences only ; but instances have multiplied. A 

 remarkable one has been furnished by Governor A. Morris, of the Korth- 



