314 EEPOKT OF THE COlBiiSSIONEK OF AGEICULTUEE. 



selection of the plants in-whicli tliey oviposit is uncertain, but that those 

 of grande do, to a marked degree, there is every reason to believe. 



During the ovipositing season of 1884, and also that of the present 

 year, when the females of grande were very abundant over those ]):irt- 

 of the wheat fields where the grain was very thin, scarcely any conld be 

 found where the plants were thickly set. 



"When the plants stand at a distance from each other there is a tend- 

 ency to throw out large, strong, vigorous "stools" slightly less advanccil 

 tlmn the main plant, and these are, to a very notable extent, selected by 

 the females in which to oviposit, but, contrary to an opinion e.\i)ressi'd. 

 ill our report last year, they invariably choose the upper joint from fir-st 

 to last during the season. 



This seems the proper place to present some facts bearing upon The 

 date of oviposition, and the relation that the two species sustain toward 

 each other. And in this we do not wish to be understood as doing more 

 than arrange the facts, to the best of our judgment, in their proper posi- 

 tion with reference to these two questions, and therefore not expressing 

 any opinion on our part as to what the results of future studies may or 

 may not prove. 



"Whatever bearing the fact of grande having been found in spring, in 

 the larval stage, in wheat sown late the previous autumn, may have 

 on the matter, it seems to us it is largely, at least, in favor of spring 

 oviposition. 



It is nowise probable that the parent female could, in the fall, dis- 

 tinguisii between a plant that would survive the winter and one that 

 would not, particularly if the winter was one of unusual severity, as was 

 the case with that of 1884-'85. So, then, we might reasonably expect that 

 those plants that failed to survive would contain very nearly their pro 

 rata of larvre or eggs, it is immaterial which, as all larvte would, it seems 

 to me, sooner or later perish of starvation. If, as was the case last win- 

 ter, from 25 to 75 per cent, of the plants failed to survive, we might 

 reasonably look for a notable decrease in the number of adults that 

 would emerge, whereas they were, if anything, more abundant the 

 present season than they were during the preceding. Then, too, if the 

 eggs had been deposited in autumn, the larva3 would have been found 

 in plants suffering from various degrees of injury by reason of the 

 severe winter, while with industrious searching they were not bo found. 

 But, allowing the females of early spring to possess the same sense of 

 discrimination that is shown by those appearing in June, we should 

 expect them to oviposit, not in the largest and toughest plants, but 

 rather in the tender, vigorous stools, just where I found the larvaj, pupa^., 

 and adults, as previously stated. 



Again, even though we admit grande to be the offspring of trUici, 

 there are not enough facts at hand to indicate that, in this latitude, at 

 least, enough emerge in the faU to produce the former species in any 

 such numbers as appeared in June. 



On the other hand, the adults could not have emerged the presrnt 

 year much prior to the 25th of March j in fact, the snow had hardly dis- 

 appeared from the fields by the 15th. This would give ua a period of 

 a little over two months intervening between the emerging of the mother 

 insect and the appearance of adult progeny. 



That during the earlier part of this period the temperature was at 

 times quite low is shown by the following table taken from the records 

 of the signal station at Purdue University : 



Average mean dailv temperature of last fifteen days of March, 1885, 

 290.82 ; same for first'iifteen days of April, 43o.05 ; same for last fifteen 



