LIBRARY

HEMIPTERA 335
.. the same species. Pulverulent, or with white wax tufts, or shining,
smooth, hairy, or tuberculate. Usually active throughout life, but
some species become scale-like or aleyrodiform and are fixed after the
first molt. Active forms may drop when disturbed and feign death for
some time.
2. Winged parthenogenetic individuals - usually migrants, which serve to
distribute the species. Normally darker than the aptene and particularly
with black portions on the head and thorax and appendages and
dark markings on the abdomen. Antennre may have many secondary
sensoria. Usually active and may jump and fly readily if temperature
is sufficient.
3. Sexual Females - usually apterous individuals normal in size or extremely
small. Abdomen often drawn out posteriorly into a long tapering
tube. Hind tibire normally swollen and with few or many sensorialike
areas. Antennre with primary sensoria. Rather inactive. Often
darker than parthenogenetic females. Most abundant in the fall.
4. Males - apterous or winged but in either case much the same. Minute
to very small. Often much darker in color than other members of colony.
Active, with very many sensoria on antennal segments III to VI.
Genital plate conspicuous. Penis often extended downwards. Most
abundant in fall.
As many as 10 or 13 generations may be produced within a year. Populations
which have not been reduced by the many natural means (fungi, bacteria,
parasites, predators, heat, cold, and other climatic factors) may become enormous
and may very seriously injure or completely destroy agricultural crops.
A number of species, chief of which is Myzus persic(£ (Sulzer), carry serious
plant diseases which make them even more formidable as economic pests.
As a group they feed upon a wide variety of plants and infest the leaves,
stems, living bark, fruits, and roots. They cause deformations on the roots and
branches, oddly shaped galls on the stems and foliage, and pseudogalls on the
leaves. They excrete quantities of honeydew which is deposited as very fine
droplets over the plants and objects beneath. This sweet, sticky substance
may collect in considerable quantities and become quite annoying. It is sought
by ants, bees, flies, aod many other insects. Ants are noted for their attendance
upon aphids, which they protect, transfer to some extent from host to host,
and stroke with their antennre for the honeydew. A black smut fungus also
grows on the secretion which makes the presence of aphids the more objectionable
in gardens, parks, and on street trees. About' the only good thing that can
be said for aphids is that they are an important article of diet of many small
attractive birds such as the chickadees, warblers, sparrows, and flycatchers,
and of many ladybird beetles, syrphid flies, wasps, and parasites.
COllecting. - Aphids may be collected and preserved in 70 per cent alcohol
for an indefinite time by submerging cotton-plugged vials in a tight jar of
the preserving fluid. From time to time the jars may be replenished if
necessary.