8 INSECTS AFFECTING VEGETABLE AND TRUCK CROPS. 



Avliat better than in dried siieciniens. It is singular that this park 

 should have been so badly infested by this species, Avhile only one 

 IndiA-idual coidd be found in a long search on the grounds of the 

 De]iartnient of Agriculture. The difference in distance is not more 

 than H miles. 



TIIK Sl'IXACir FLEA-I5EETLE. 

 (Diftonychu .ranthomcl(rna Dalm.) 



During the year 1D1"2 beets as well as spinach grew very rapidly 

 in the District of Columbia during rainy days, succeeded by warmer 

 ones, but owing to press of other work the writer was unable to give 

 them and their insect enemies as much personal attention as theT 

 deserved, and another reason was that the species involved, Disonijeha 

 xanthoonelcena Dalm.. has already been written up with considerable 

 care. 



Nevertheless there is always something new to learn, as there will 

 be of all species, as long as we continue to observe them under dif- 

 ferent environments and atmospheric conditions. The table beets 

 grew so rapidly that in spite of the larva:' and adults of the spinach 

 flea -beetle, which " peppered them full of holes," they made consid- 

 erable progress. 



The spinach began to die rapidly about the beginning of the third 

 week of June, and in four days nearly every plant appeared as if dying. 

 In addition to the spinach flea-beetle, the spinach aphis {Rhopalosi- 

 pJinm dlanthi or Myzus persica' auct.) was also present, but, as 

 affirmed by Dr. Erwin F. Smith, who, with the writer, examined 

 the plants June 25, there was no evidence of disease or of malnutri- 

 tion. If the plat of spinach had been a field, the plants would tm- 

 doubtedly have perished, owing to the combined attack of the flea- 

 beetles and the aphides, and this in spite of the fact that the aphides 

 were being raj^idly destroyed by ladybirds. 



To determine the extent or degree of injury, comparison was made 

 of a beet root taken from our experimental jilat. Avhich had l^een very 

 little affected by this flea-beetle, with another lot which had been 

 badly affected, with the result that it required nine of the affected 

 roots to equal the weight of one that was practically imaffected. 

 The small roots were picked out at landom by the writer from the 

 place most badly affected, which was at the sunny end of the plat. 



It should be mentioned in this connection that plants growing 

 where they were shaded by hedge plants were comparatively little 

 affected 1)V insects. This same o!)servation has been made in connec- 

 tion with the imported cabbage caterpillar {Pontia rapa' L.), which is 

 not disturbed by wasps when feeding in shady places. 



