88 Farmers’ Bulletin 1128. 
whereas cool, cloudy weather seems to reduce the activities of the 
parasitic and predacious enemies, permitting the aphids to become 
correspondingly abundant. 
Ladybird beetles (fig. 29) may be found in almost any colony of 
aphids, both the beetles and larve feeding freely on the insects. 
Numerous species of these 
beetles attack the aphids, and 
they should be protected and 
encouraged when possible. 
Larve, or maggots, of syr- 
phus flies, also called sweat 
fhes (figs. 30and 31), are very 
generally present in aphid 
colonies and are most impor- 
Fia. 29.—The convergent ladybird (Hippodamia conver- SLAY 
gens), an enemy of orchard aphids: a, Adult; b, pupa; tant checks to their increase. 
c,larva. Enlarged. (Chittenden.) The larvee of two or three 
species of lacewing flies feed freely on aphids, although they are not 
so important as the insects mentioned above. 
Probably the most important check to aphid increase, however, 1s 
the work of certain minute, four-winged flies which live parasitically 
onthe aphids. These multiply very rapidly and under normal condi- 
tions are very effective. The bodies of parasitized aphids usually 
become enlarged, assume a more or less globular 
shape, and finally show the exit hole of the adult 
parasite. (Fig. 32.) 
CONTROL MEASURES. 
As previously stated, aphids feed upon plant 
juices which they obtain by means of a beak 
inserted into the plant tissues. Paris green, arse- 
nate of lead, and other arsenicals, or stomach 
poisons, are therefore ineffective against these in- 
sects, and the so-called contact sprays, such as 
kerosene emulsion, soap washes, nicotine sprays, 
etc., must be employed. These sprays, to be 
effective, must come in contact with the bodies 
of the insects, and great thoroughness in spray- 
ing is necessary. 
Two principal plans of attack may be followed Fic. 30—Larva of the syr- 
- . : phid fly <Allograpta obli- 
in the control of orchard aphids. Those species ja, an important onemy 
which winter in the egg stage on the plants to be esses tote; en 
protected may be treated with sprays early in the ~~ © 
spring as the buds are expanding, to destroy the young stem-mothers. 
Treatment at this time assumes that without it the aphids would 
become injurious later in the season and is in the nature of insurance. 
ee 
