5 
insects produced each day, which is six, one individual would become 
the progenitor of 425,912 of these aphides in one season. 
NATURAL ENEMIES. 
The efficiency of natural agents in the destruction of aphides is so 
well known that it has been hoped that some one or more of the many 
species observed to attack the pea aphis would increase in such num- 
bers as to have the effect 
of limiting its multipli- 
cation. In spite, however, 
of the closest observation 
by a number of persons, 
the natural enemies have 
been found to produce 
only transient relief, and 
this only in limited areas, 
as a rule late in the season 
after damage has been ac- 
complished. Fic. 2.—Spotted ladybird (Megilla maculata): a, Larva; 
The present list of in- 2, empty pupal skin; c, beetle, with enlarged antenna 
5 above. Allenlarged. (Author’s illustration.) 
sects known to attack this 
aphis includes seven species of ladybirds, or “‘ladybugs’ 
familiarly termed,! three species of syrphus flies,? a lace-wing fly,? a 
soldier beetle, and a few minute four-winged hymenopterous parasites.° 
The ladybirds are destructive both as beetles and larvee; the syrphus 
flies only in the larval condition, which is true also of the lace-wing fly. 
The efficiency of the syrphus flies is greatly impaired by the presence 
of a braconid parasite,® which is sometimes very prevalent, almost com- 
pletely exterminating its hosts in many fields. Nearly all the species 
observed are well-known enemies of other aphides, and in fact greatly 
prefer as hosts the cabbage aphis and species found on weeds to the 
pea aphis. The spotted ladybird (Megilla maculata DeG.) and a lace- 
wing fly (Chrysopa oculata Say) are shown in their different stages 
in figures 2 and 3 respectively. 
In addition to the natural enemies that have already been enumer- 
ated, several other insects attack the pea aphis, among them a small 
red mite, Rhyncholophus parvus Banks. 
) 
as they are 
1 Coccinella novemnotata Hbst., Hippodamia convergens Guér., Megilla 
maculata DeG., Hippodamiaglacialis Fab., Adalia bipunctata L., Hippoda- 
mia 13-punctata L., and Coccinella sanguinea L. ? Allograptaobliqua Say, 
Syrphus americanus Wied., and Spherophoria cylindrica Say. *%Chrysopa ocu- 
lata Say. 4 Podabrus rugosulus Lec. ° Aphidius washingtonensis (Ashm. 
MS.?), A. fletcheri (Ashm. MS.?), Praon cerasaphis Fitch, Isocratus vul- 
garis Walk. ® Bassus letatorius Fab. 
In the above list the species of each class are named in approximate order of 
abundance in Maryland, Virginia, and the District of Columbia, and consequent 
efficiency as destroyers of the aphis in that region. 
A6—49 
