^Jg 



increase in such numbers as to have an effect upon limiting its niulti- 

 pHcation. In spite, however, of the closest observation by a nunil)er 

 of persons, the natural enemies have been found to produce only tran- 

 sient relief, and this only in limited areas, as a rule late in the season, 

 after damage has been accomplished. 



The present list of insects known to attack this plant-louse includes 

 seven species of ladybirds, or "lady bugs" as they are familiarly 

 termed,^ three species of syrphus Hies,^ a lace-winged fly,^ a soldier 

 beetle,"* and a few minute four-winged hymenopterous parasites.'' 



The ladybirds are destructive both as beetles and larva' ; the syrpbus 

 flies only in the larval con- 

 dition, which is true also of m ^, \ , \ ^''='=ts»:^ 

 the lace-wing fly. The ef- 

 ficiency of the syrphus flies 

 is greatly curtailed by the 

 presence of a Braconid par- 

 asite,** which has been very 

 prevalent during the last 

 two seasons, sometimes al- 

 most completely extermi- 

 nating its host in many 

 fields. Nearly all of the 

 species observed are well- 

 known enemies of other 

 plant-lice, and in fact greatly prefer as hosts the cabbage plant-louse 

 and species found on weeds to this pea louse. The spotted ladybird 

 {Megilla macnlata) and a lace-wing fly (Chrysopa ornhiin) are shown 

 in their different stages in figures 2 and 3 respectively. 



In addition to the natural enemies that have already l)een (jnumer- 

 ated, several other insects attack this pea louse, among others a small, 

 red mite {Rhyncliolophus parvus Banks). 



Considering the inefficiency of all other natui-al agencies, if we except 

 atmospheric conditions, in the control of this pest, it is hoped tliat a 

 common fungous disease of plant-lice, known as Empusa aphidis, may 

 become an important factor. As the development of this fungus is 

 dependent upon rather warm, humid weather and is retarded by drought, 

 it is fairly certain that atmospheric conditions, after all, are most 



Fia. 2.— Megilla maculata : n, larva ; ^. empty Mipalskiii; 

 c, beetle with onlargeii antenna above— all enlarged 

 (author's illustration)- 



' Coccinella novemnotata, Hippodamia convergens, Mefjilla iiiKciihdn, Hippo- 

 dnmin (jlacialis, Adalia bipunctata, Ilippodnmia 13-pnnctaia, Coccinella san- 

 gninea. - Allograpta ohliqnn, Syrphus umericana, SpharopJioria cglindrica. 

 '■^Chrysopa oculatn. ^ Podalmis rHgosuliis. ■'Aphidiiis. washinglonrnsis, A. 

 fU'.tcheri, Fraon ccrnsaphis, Isocratus vulgaris. ''Bassus lectorius. 



In the txbove list the species of each class are named in approxinmte order of 

 ahnnchmce in Maryland, Virginia, and District of Columhia, and onnsccincnt 

 etlicieiicy as destroyers of the plant-lonse in that region. 



