SMfTHSONIAN INSTITUTION LIBRARIES 



THE ALFALFA GALL MIDGE 



3 9088 01272 8168 



as late as October :2<j. This late date would indicate an emergence 

 in spring, rather tlian in late fall, under natural conditions. 



OBSCURITY SUBROUNDING ITS APPEARANCE. 



That the insect should first make its appearance in the midst of a 

 desert country (see fig. 6) is somewhat surprising. There is nothing 

 known of it that would lead us to believe that it can be distributed in 

 alfalfa seed. It could hardly have been imported accidentally from 

 the Eastern Hemisphere into this part of the country. Besides this, 

 it is preyed upon extensive!}' by parasitic insects, which would imply 

 a rather long residence in this country, although as these parasites are 

 all new to science and have never been described, 

 it would almost seem that it might be working its 

 way from Mexico northward. The abundance 

 of these jDarasites is an encouraging feature, as 

 they tend to prevent its becoming destructive. 



^Vith the additional information w^hich we 

 hope to obtain, both from investigations of the 

 bureau and from those into whose hands this 

 circular may fall, we shall probably be able to 

 disjjel much of the obscurity at present sur- 

 rounding the pest. The indications are that it 

 is spreading over the alfalfa-growing sections of 

 the extreme Southwest, but it does not neces- 

 sarih' follow from this that it will prove so 

 destructive as have many other insects coming 

 to us from across the Atlantic Ocean. 



PREVENTIVE MEASURES. 



It is 3'et too early to say much concerning measures for preventing 

 injury by the alfalfa gall midge. Of course, mowing the alfalfa just 

 as the plants are coming into bloom will doubtless keep the numbers 

 of the midge much reduced, as this method tends to prevent develop- 

 ment, and, therefore, to curtail uicrease in numbers. A significant 

 observation made at Sacaton, Ariz., Ma}^ 27, 1911, by Mr. Smyth, is 

 quite suggestive. "The galls were found very sparingly in fields 

 vrhich had been cut for hay less than two months since, and in such 

 fields from none of the galls had the adults issued. But in one field of 

 both purple and j^ellow flowering alfalfa, which had not been from 

 early spring at any time cut for hay, but rather allowed to run to 

 seed, the galls were far more plentiful than in other fields, and from 

 a large percentage of them adults, or parasites, had issued." 



Approved : 



James Wilson, 



Secretary of Agtncidture. 



Washington, D. C.. January 4, 1912» 



O 



Pig. 6. — Map showing 

 localities where the 

 alfalfa gall midge has 

 been found in the 

 United States. (Orig- 

 inal. I 



