The Garden Magazine, April, 1920 
101 
to Oats and certain other grasses, 
where it has to be reckoned with as 
one of the most serious of our grain 
pests. Another species uses the Clover 
as a summer resort — and for a change 
in diet — after having wrecked the leaves 
of theorchard it has inhabited earlyinthe 
season. The insect famous in economic 
literature as the Hop aphid or Hop- 
plant louse winters on the garden Plum, 
as does a second species which migrates 
to Thistles, and a third which eschews 
the country for the greater refreshment 
of a watering place during the hot 
months — in other words a residence 
aboard an Arrow-head or certain other 
succulent plants (See The Garden 
Magazine, December, 1917) where it 
enjoys a more or less complete change 
of scene and diet. 
S' 
APPLE APHIS ON THE ELM 
The “spring migrants” move into summer quarters on the 
leave the summer food plant and take flight — back to some 
American Elm. 
Alighting on the bark, they seek a convenient crevice and 
give birth to minute young, part of which are egg-laying females 
and part males — this being the only time in the life cycle of this 
insect that either of these forms is produced. These tiny “true 
sexes” have no functional mouth parts and do not eat, their 
chapter in the life history being concerned merely with mating 
and providing for the deposition of the over-wintering egg. 
Each female lays but one of these, the single egg nearly filling 
her small body. 
This egg is the closing page of the life cycle for the fall, and 
the opening one in the spring; because it is from this over- 
wintering egg that the stem-mother hatches at the time of the 
bursting leaf buds, in season to form the rosette of Elm leaves 
for the spring habitation of herself and 
her numerous progeny. And startling 
as this life-round may seem, it is no 
isolated example, for the histories of 
many species of this family of insects 
are most dramatic! 
O THE man who innocently plants 
Lettuce near his or his neighbor’s 
Currant bushes is simply making mat- 
ters convenient for one of the aphids 
migrating from Ribes to members of 
Apple the Compositae — and correspondingly 
difficult for the person who washes the 
salad, for the leaf-green bodies of the apterous summer forms 
of this species blend so well with the color of the Lettuce that 
detection is almost impossible — and the insects cling more- 
over, amazingly. 
All this considered, it is small wonder that the gardener ex- 
claims, “where do these insects come from?” upon seeing aphid 
colonies thriving where a few days before there were none; and 
the question has as many answers as there are migratory species. 
Which may seem distracting, though the knowledge is an ad- 
vantage, for reference to the accompanyingtable will suggest that 
not infrequently the dual personality of these remarkable insects 
gives a double chance at their control; while with certain of 
them, on the other hand, their opportunities of escape are 
twofold because of added difficulties presented by their com- 
plex existence. 
T AKE that Elm leaf with a rolled- 
under edge, for instance, hanging 
on the branch not far from the rosette 
just discussed. That leaf holds a story 
as interesting as the one just told and 
much like it, except that its spring 
migrant seeks, instead of the Apple or 
Hawthorn, the Juneberry or Shad-bush, 
on the underground stems of which its 
summer colonies dwell. And the simi- 
lar rolled-under leaf of the English 
Elm shelters an aphid that migrates 
to the Currant to pass the heated 
term. 
Nor are the Elms alone in serving 
as winter and early spring residence 
for aphids who spend their summers 
in other parts. Among the common 
spring leaf-feeding aphids which winter 
in the egg stage on the Apple, for in- 
stance, the migrant of one takes flight 
WHEN SUMMER COMES 
A colony of woolly aphis that left the Elm and is established in its summer home on the Apple 
