MEXICAN ("ONCHUKLA IN WESTERN TEXAS IN litOf). 13 



lioppordozor with a rev()lvin<i- fan, convinced the Avriter of the ])rac- 

 ticahility of collecting these insects mechanically. The great major- 

 ity of the insects, when undisturbed, may be found near the tops of 

 the plants, on the seed clusters when these are present. They drop 

 to the ground when slightly disturbed, much more readily, in fact, 

 than when they have a footing on a more substantial object like a 

 cotton boll. It is safe to jDredict that a contrivance for collecting Avill 

 be devised when the necessity arises. It should be light, operated 

 fr(»m behind, and consist essentially of an elongate metallic pan sus- 

 pended below a revolving fan geared to the supporting wheels. 



I'HEVEXTIVK AND PROTECTIVE MEASURES. 



If, as advised in one of the i:)receding paragraphs, no attempt is 

 made to produce a seed crop during the period of the year when the 

 conchuelas are dangerously abundant, an important factor in their 

 nuiltii)lication and spread will be eliminated. But the shorter period 

 required for the hay crop is sufficient to permit the insects to reach 

 the enormous numbers indicated in the writer's reference to the occur- 

 rence on alfalfa in northern Mexico in 1905. Uusually the greater 

 number of the insects Avill not reach maturity during the interim be- 

 tween cuttings, and the work of preventing the spread will be in part 

 the checking of the migration of the craAvling nymphs. This can be 

 readily accomplished when necessary by leaving an uncut border 

 around the field, where the insects when trapped can be destroyed by 

 spraying with kerosene emulsion. As the insects show a marked 

 tendency to concentrate in certain limited areas rather than to spread 

 evenly over the fields, this can be taken advantage of by making a 

 general examination of the field, before cutting, to locate the colonies. 

 A few small bo^'s in a few hours might pick up several quarts " of the 

 adults wdien these are abundant and well concentrated. If this is not 

 feasible, small heavily infested areas ma}^ be treated with kerosene 

 emulsion, although adult pentatomicls are apt to be quite resistant 

 to this insecticide. At Tlahualilo, Durango, Mexico, on JuW 11, 

 1905, after the alfalfa hay had been made and stacked, countless 

 hosts of the insects still remained in the alfalfa field in spite of the 

 extensive migration to neighboring crops. Those that remained 

 were largely concentrated near one corner of the field and, as suitable 

 spraying apparatu^j was not available, destruction of the j^est was 

 accomplished by respreading about 3 or 4 tons of alfalfa hay over 

 the ground and then burning it. This operation for the protection 

 of the surrounding cotton fields against further invasion from this 

 source was effective, but would be unnecessarily costly under ordinary 



"One quart contains approximately 1,500 adult specimens of P. ligata. 



