1900 ] ENTOMOLOGICAL SOCIETY. lOi 



brush the vines backward and forward ahead of the Iron Age cultivator, drawn by one 

 horse, and in this manner the insects are covered and a very large propartion of them 

 destroyed. The cultivation should not be repeated until the third day, as it requires 

 usually something over forty-eight hours for the destruction of the adult insects when 

 covert d with earth. On this plantation we also sprayed a large acreage to show the 

 practical side of this work. Suffice it is to say that we have found that no spray can be 

 used which can destroy a percentage of insects large enough to warrant the expense of 

 the operation. In this instance we sprayed 100 acres in two days, and thoroughly tested 

 the method from every standpoint, using various materials. We abandoned the spraying 

 apparatus, and began the brush and cultivator method, which was followed up persist- 

 ently, with the results already noted. We have also used the " brush and pan," in 

 which a bushel of lice were caught to each row of 125 rods long. 



Many natural enemies, such as parasitic and predaceous insects, have been found 

 feeding upon this pest in the fields, and in this manner, no doubt, the number has 

 been somewhat reduced The mott important factor, however, we have observed in 

 the destruction of this pest has been the fungous disease, Empusa aphidis, which was 

 common during the early part of the season upon this insect, in both clover and pea 

 fields. It is a contagious disease and destroys the pest in very large numbers, under 

 certain conditions. In one instance we found 58 dead lice upon the underaurface of 

 a single lobe of a clover leaf, and it was not an uncommon thing in June to find 15 or 

 20 dead lice upon the under surface of a pea leaf. With the rains which prevailed 

 throughout this section cf country during June, which fostered the developement of the 

 disease, it spread rapidly throughout the infested fields, and as a consequence it was very 

 difficult to find the pea-louse upon late peas. A careful examination of peas where the 

 insects were abundant in June showed that they were practically free from them. We 

 feel, therefore, that the climax, as far as the development of thn insect this season, has 

 been reached, and that these silent factors m nature are now actually reducing the pest 

 to such a point that it may possibly be several years before it will be such a destfuctivo 

 pest in this section as it has been for the past tr-o seasons. At any rate, the conditions 

 are such that the farmer and canner have new hope, and we trust the future will bring 

 fewer lice and more peas. 



In discussing the paper. Prof. Hopkins enquired whether the insect were possibly an 

 introduced species, and if there were any records of its previous occurrence in large num- 

 bers. 



Mr. Johnson replied that, in his opinion, it was not an introduced pest, but an indi- 

 genous insect, which had multiplied enormously from the change of conditions. The only 

 record he had regarding it was one made ten or twelve years ago by Mr. Beckwith at the 

 Delaware station, and another of its occurrence along the Potomac River in 1887. In 

 neither case, however, was it certain that it was the same inspct, as no specimens had 

 been preserved. The pea-growers state that the insect has been known to them for many 

 years. 



Prof Hopkins said that this case is such a complete parallel to the invasion of the 

 pine-bark bfetle, the trouble from which is now over, that it occurred to him that in this 

 case, v-ithin the next few years, this insect will proba>>ly disappear or become exceedingly 

 rare. He had taken the trouble, in connection with the investigation of the pine insect, 

 to look np the history of invnksions by indigenous insect?, and found that they multiply 

 rapidly for several years, become enormous'y destructive, and a few years later disappear. 

 They are destroyed by parasite-s or by clim»tic conditions and soon become rare species. 

 This happened in the case of the pine insect, which was scarcely heard of before, and was 

 one of thu rarest insects in collections until it suddenly occurred in 1891 in such enormous 

 numbers as to destroy millions of dollars worth of timber, but now it is practically extinct. 

 Not a single living specimen has been found since the fall of 1892. Prof. Johnson's piper 

 shows the great importance of the work he has undertaken, and his experience will be of 

 inestimable value in dealing with future outbreaks of the pea louse. He thought the 

 farmers of Maryland would make a great mistake by changing their locations for growing 

 peas until perhaps a year had elapsed, because if the rule follows in regard to sudden 

 invasions by indigenous insects they will soon disappear or become rare. 



Mr. Johnson said he was greatly obliged to Mr. Hopkins for his opinion, but there 

 is so much money at stake that the growers could not let the matter rest awaiting nature's 



