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University of I.Viizioii; 


Glen S. Winterri 



No. 1. Story of Illinois: Indian and Pioneer, by V. S. Eifert 

No. 2. Mammals of Illinois Today and Yesterday, by V. S. Eifert 

No. 3. Exploring for Mushrooms, by V. S. Eifert 

No. 4. Flowers that Bloom in the Spring, by V. S. Eifert 

No. 5. Invitation to Birds, by V. S. Eifert 

No. 6. Man's Venture in Culture, by Thome Deuel 

No. 7. The Past Speaks to You, by Ann Livesay 

No. 8. Common Insects of Illinois, by A. Gilbert Wright 

No. 9. American Indian Ways of Life, by Thome Deuel 

No. 10. Amphibians of Illinois, by Paul W. Parmalee 

No. 11. The Fossils of Illinois, by Carlton Condit 

No. 12. Some Plant Galls of Illinois, by Glen S. Winterringer 

Cost: 25^ each; 204 each in lots of 25 or more 

Address all inquiries to the MUSEUM DIRECTOR, 
ILLINOIS STATE MUSEUM, Springfield, Illinois 

Otto Kerner, Governor 


William Sylvester White, Director 

Thorne Deuel, Museum Director 




Glen S. Winterringer 

[Printed by authority of the State of Illinois.] 


M. M. Leighton, Ph.D., D. Sc, Chairman 
State Geological Survey, Urbana 

Everett P. Coleman, M.D. 

Coleman Clinic 

Percival Robertson, Ph.D., LL.D. 

The Principia College 

N. W. McGee, Ph.D. 

North Central College 

Sol Tax, Ph.D., Secretary 

University of Chicago 


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ho . I ^ 




Acknowledgments 4 

Introduction 5 

Historical sketch 6 

Gall producers and how galls are formed 7 

a — Insects and allies 7 

b— Plants 11 

Uses of galls 13 

Damage done by galls 14 

Suggestions for study and collecting 15 

Photographic section 16 

References 48 

Index 50 


I am indebted to Karl Bartel, of Blue Island, Illinois, for his 
contribution of fine photographs. Many other photographs by Charles 
Hodge and John Gerard have added to the usefulness of this pub- 
lication. Line drawings are the work of Jeanne McCarty Kains and 
the cover was designed by Betty Carroll. Helpful and constructive 
suggestions were made by Thorne Deuel, Paul Parmalee and Milton 
Thompson of the Museum staff. Special thanks are due Lewis J. 
Stannard of the Illinois Natural History Survey for his critical ex- 
amination of the manuscript. I am very grateful to Orvetta Robinson 
and Charles Hodge for assistance with preparation and arrangement 
of the photographs and without whose help this booklet would have 
been difficult to complete. 

A number of sources have been used for information contained 
herein. The publications are included in the list of references. Special 
use, for identification, was made of plant galls and gall makers 
by E. P. Felt, Comstock Publishing Co., Ithaca, New York. Per- 
mission granted by several publishers to redraw certain figures is 
appreciated. Fig. 1, No. 2 is redrawn from Kinsey, the origin of 
HIGHER CATEGORIES IN CYNIPS, page 89, permission of the Depart- 
ment of Zoology, Indiana University. Fig. 1, Nos. 1, 3, and 4 are 
redrawn from Comstock's an introduction to entomology (9th 
revised ed.), pages 411 and 423. Fig. 1, No. 6 is redrawn from Com- 
stock, Comstock and Herrick's a manual for the study of insects, 
(revised ed.), page 19, by permission of Cornell University Press. 
Fig. 1, No. 5 is redrawn from Metcalf and Flint's destructive and 
USEFUL insects, (2nd ed.), page 232, permission of McGraw-Hill 
Book Company. Figs. 2 and 3 are redrawn from Kinsey, the gall 
wasp genus cynips, frontispiece and page 511, permission of the 
Department of Zoology, Indiana University. 

Photograph credits are indicated by initials in parentheses fol- 
lowing the captions as: Karl Bartel (KB), Charles Hodge (CH). 
John Gerard (JG), and Gordon S. Smith (GSS). 


Galls are abnormal growths of plant tissue often found on roots, 
stems, leaves, flowers and seeds. These growths result from a stimu- 
lus supplied by external sources. These sources are generally in- 
sects or, in some cases, fungi, viruses, bacteria, nematode and eel 
worms, and perhaps other agents. 

Galls and gall insects, as well as the other organisms which 
stimulate their formation, may be found all over the earth wherever 
the host plants are growing. This does not mean that the range of 
gall insects and other organisms coincides exactly with the range of 
the host plants. To the botanist galls are interesting because they 
represent abnormal plant growth. He wishes to know more about 
the insect secretions and their effects on growing plant tissues which 
are important in studies of plant physiology and anatomy. The 
entomologist is concerned with the life cycles of gall insects and the 
variations in form shown by many of these insects. Home gardeners 
and horticulturists wish to know how to recognize and control the 
galls which cause damage to landscape plantings. 

There has been no attempt to include, in this booklet, all of 
the thousands of kinds of known galls. Only those commonly seen 
in Illinois have been photographed and described. A list of refer- 
ences is provided for use of those who become interested in further 
studies of galls and gall insects. The Latin or scientific names of 
both galls and insects are based largely on terminology used by E. 
P. Felt in plant galls and gall makers, (Comstock 1940). In the 
gall photographs the common name is given first, followed by both 
common and scientific names of the gall insect which produced it. 
The common and scientific names of the plant upon which the gall 
was found are also included. This arrangement of information has 
been used for all of the gall photographs in the booklet. Plant de- 
formities are not usually given scientific names; hence the name of 
the insect which caused the deformed plant tissue is also the name 
of the gall. 

Group names are often used in identification of galls such as: 
rosette, oak apple, bud, leaf, bullet, roly-poly, and pouch. Galls 
may be classified by the plants upon which they are found in which 
case we might refer to maple leaf, goldenrod, oak, hackberry, elm, 
willow, and sunflower galls. 

It is hoped that this publication will stimulate an interest in 
those outdoor activities which will lead to the discovery of galls and 
gall insects. 


Plant galls and gall insects are not a recent discovery. They 
were observed during the time of ancient Greek and Roman natural- 
ists and historians as shown by recorded works. We do not know 
that galls were actually named as such by the earliest writers, but 
they surely observed malformed growths on plants about which 
they did write. Theophrastus (372-288 B.C.) is credited with at 
least two important botanical works, one with the title a history of 
PLANTS and another the causes of plants. Pedanios Dioscorides 
(40-90 A.D.) was a Greek who wrote about plants mainly from a 
medicinal standpoint, and his materia medica contained many de- 
scriptions of plants used in early medical practice. Pliny the Elder 
(23-79 A.D.) was a Roman naturalist who described plants in his 
NATURAL HISTORY. Through these past centuries the writers were 
interested in uses of plants rather than in their abnormal growths. 
However, in the seventeenth century Marcello Malpighi, an Italian 
physician, included an account of plant galls in his anatomia plan- 
TARUM. It is not known with certainty that Malpighi established the 
final relationship between an insect and the gall it produced on a 

During the Middle Ages galls were associated with superstitions 
and omens in foretelling future events. This was often accomplished 
by observing various types of grubs as well as adult insects found 
inside a gall. All insects found in a gall may not be responsible for 
its formation, for some are "guests"; others are transients or even 
parasitic insects which devour the gall-former. Thus insects in a 
gall, phases of the moon, and signs of the Zodiac may have been 
considered important to those attempting to foretell future events 
but they did very little to advance a study of relations between in- 
sect, plant, and the gall. 

At the present time galls, insects, and the host plants are con- 
sidered important enough to be the subject of research in scientific 
institutions. Dr. William Hovanitz, in his studies at Earhart Plant 
Research Laboratory of the California Institute of Technology, has 
used sawflies and willow leaves in experiments to discover what 
actually goes on during the formation of plant gall tissue. Gland- 
ular fluid produced by larvae and adults of these sawflies has been 
analyzed in an attempt to find the activating substance which causes 
plant cells to multiply rapidly in its presence. So from ancient 
days to the present both galls and insects continue to capture the eye 
and the mind of man. 



(a) Insects and Allies 

In this booklet we are concerned with those insects known to 
produce galls illustrated in the following pages. In Fig. 1 the draw- 
ings intend to illustrate, in a general sense, what is meant when we 
refer to such typical gall insects as: jumping plant louse, gall wasp, 
aphid nymph and adult, gall gnat, and pear-leaf blister mite. Less 
important gall insects such as: long-horned beetle, gall moth, and 
other kinds of mites could be added to the list. Mites are not true 
insects but are more closely related to spiders. Many other insects 

5 ^ ^ '6 

Fig. 1. A Group of Gall-producing Insects Very Much Enlarged. 

1. Adult jumping plant louse, Pachypsylla celtidismamma (From Packard). 
2. Female gall wasp, Cynips (From Kinsey). 3. Aphid nymph, Colopha ulmi- 
cola (From Riley). 4. Adult, winged aphid Colopha ulmicola (From Riley). 5. 
Male gall gnat, Hormosomyia oregonensis (Froni Cole fit Lovett). 6. Pear-leaf 
blister mite, Eriophyes pyri. 

may be gall producers and only study and observation will reveal 
them. Insects assigned to the Order Hymenoptera, a very large 
group in which bees and wasps are included, are highly specialized. 
By specialized we mean that certain parts of their bodies are well 
adapted for doing special work in collecting pollen, cutting leaves, 
collecting mud particles, and constructing honeycomb. Dr. Alfred 
Kinsey made excellent and extensive studies of particular gall wasps, 
and references to some of his works are given at the conclusion of 
this booklet. 

Female insects often possess an ovipositor which is made up of 
modified or specially shaped abdominal segments. By means of this 
ovipositor the female can pierce tender plant tissue and deposit an 
egg. As the egg is pushed into the cells of the plant tissue, a small 
amount of the insect's body fluid accompanies the egg and thus 
enters some of the plant cells. Dr. Hovanitz, in his studies, found 
that female sawflies whose ovipositor merely broke the tissue of 
willow leaves used in the experiments did not produce gall growth 
at all. Those sawflies which did inject some body fluid, but had not 
deposited an egg, stimulated the beginning of gall development. 
Hovanitz also observed that areas of a willow leaf in which fluid 
from the insect was present differed from those areas in which an 
egg was also present only in size of the gall-growth region. Recent 
experiments and investigations show that the glandular fluid pro- 
duced by the adult insect as it deposits an egg, and by the larva 
which develops from the egg, is the stimulus which starts abnormal 
plant growth and the formation of a gall. It must always be kept 
in mind that the living plant cells into which the insect fluid is in- 
jected play an important part in the final form and shape of the gall. 

The similarity of the glandular secretions of adult and larval 
insect has not been proved, but they are thought to be very much 
alike. These secretions are chemically complex substances of high 
nucleic acid-protein content and have been difficult to analyze. The 
presence of a virus or a fungus may require investigation and con- 
sideration in gall formation. However, these agents and their in- 
fluence must await further research. 

Fig. 2. Very Much Enlarged Drawing of a Cecidomyid Larva. 

The larvae or grubs of many gall insects are most important in identifica- 
tion. The drawing is intended to show at (a) the presence of a "breast bone" 
which is an identifying mark of the cecidomyid (midge) larvae. The larvae of 
cynipids (gall wasp) do not have the "breast bone". Thus by examination of 
gall grubs one can separate at least two large groups of gall insect larvae by 
the presence or absence of this "breast bone". 

^ ' 




Fig. 3. Explanation of Alteration of Generations. 

Part "A" of the diagrammatic sketch is the sexual generation of gall and 
gall insect. Both male and female wasps (2) grow from larvae hatched from 
eggs which are deposited in the bud of white oak (1). The tiny galls are found 
on the inner bud scales (1). In late May or early June the adult wasps (2) 
emerge and mate. The female wasp then lays eggs generally along the midrib 
or main veins of a white oak leaf upon which the Hedgehog Gall develops (3). 

Part "B" is the asexual or agamic generation of both gall and gall insect. 
The Hedgehog Gall on a white oak leaf (3) grows and contains a fertilized egg 
laid by a female wasp. In early autumn larvae from these Hedgehog Galls pro- 
duce agamic or asexual females. These agamic wasps (4) then lay unfertilized 
eggs in buds of white oak late in October or early November. The following 
spring both male and female wasps will develop from larvae in the bud scale 
galls and the cycle begins again. 

Most gall insects, if one includes the total range in size, are 
small and fragile. They would seem small even if you looked at 
one on the tip of your finger. The insects and their life histories 
are as fascinating as the variations in gall forms themselves. Gall 
insects, besides being small, may have their appearance changed by 
several other factors for example: (a) sex differences in which the 
male can be distinguished from the female, (b) variations, (c) muta- 
tions, and (d) alternation of generations (Fig. 3). A brief account 
of the last three of these factors will help the reader with some idea 
of their meaning. Variations occur when the insect is not exactly 
like its parents but shows some slight differences. Mutations, how- 
ever, are sudden and new variations not previously known to occur 
before in the species. Mutations may sometimes occur in the off- 
spring of both plants and animals. An explanation of alternation 
of generations, stated in simple terms, is that succeeding generations 
(in this case both the gall and the gall insect) are not alike at all 
even if slight differences are taken into account. Let us say that 
insects of one generation, instead of looking exactly like their 
parents, more strongly resemble their grandparents. The diagram 
in Fig. 3 will help to illustrate this. 

Among some gall wasps the differences between two succeed- 
ing generations is great enough to have caused them, at one time, 
to be incorrectly named as separate species or kinds. Where alter- 
nation does occur, one generation may be made up of agamic fe- 
males. The term "agamic" means that they have not developed from 
union of male and female reproductive cells, but grow from unfer- 
tilized eggs (Fig. 3 Part B). The eggs of these agamic females, how- 
ever, develop or hatch to become either male or female individuals 
(Fig. 3 Part A). The next generation, therefore, is composed of 
both female and male insects which produce eggs (female) and 
sperm (male). The young from these fertilized eggs develop into 
agamic females again and the full cycle is repeated by these al- 
ternating generations. The alternate parts of generations of both 
insect and corresponding plant gall may occur at different seasons 
of the year which makes necessary a careful study and observation 
of the erjtire life cycle. As shown in the explanation accompanying 
Fig. 3, the galls produced by alternating generations, as well as the 
insects, do not look alike and are found on different parts of the 
host plant. In 1873 H. F. Bassett is credited with having observed 
the variation and alternation of generations in galls and gall insects, 
and in 1875 Dr. H. Adler explained its true nature. 

Life cycles of some gall insect species may require four years 
for completion. In view of this time requirement there is littie doubt 
that errors in identification could have been made. A further dif- 
ficulty encountered in a detailed study of gall insects is the presence 
of "guest" flies or other "guest" insects often found inside a particu- 
lar gall. Such insects, especially the flies, do not attack the gall- 
producing individual, but make use of living space and take some 
advantage of the food supply. We must distinguish parasitic and 
predacious visitors from the "guests". When parasites or predators 
are present they may actually feed upon the larva of the gall-pro- 
ducing insect. Larvae of some gall midges, according to E. P. Felt, 


are often present in galls in whose formation they are not known to 
have played a part. The factual knowledge of the biology of many 
gall insects is not well known, and the study of their life histories 
is a challenge to both amateur and professional students. 

(b) Plants 

A gall is made up of plant cells which have been stimulated to 
undergo rapid division and growth by the presence of insect secre- 
tions. The plant therefore furnishes most of the material which 
makes up the gall while the insect supplies the secretion which 
stimulates growth. Galls develop in very young plant tissue which 
is generally found in buds or in rapidly growing tips of branches, 
(Fig. 4). These buds and growing tips are made up of unspecial- 
ized plant cells which under ordinary, normal conditions continue 
to grow into leaves, stems and flowers. Fully mature, hardened 
plant tissues are unsuitable places in which a gall insect may de- 

Fig. 4. How a Gall is Formed. 

(1) A diagrammatic sketch to show how a gall insect selects a bud in 
which it deposits an egg. (2) Enlarged drawing of a bud to show position of 
egg within overlapping scales of the bud. (3) The plant cells of the bud have 
begun to grow thus enclosing the insect egg. (4) Later stage in which a larva 
may have developed from egg. The bud is now deformed into an early stage 
of the gall. (5) The gall has matured and a larval chamber is shown in the 
center. After the gall develops, the bud no longer performs its function of 
producing normal leaf, stem, or flower. 


posit an egg. Selection of new plant growth areas by the insect is 
important for two reasons: (1) the tissue is soft and easily pene- 
trated by the female insect ovipositor, and (2) the new cells are 
generally dividing and growing. 

The different kinds of gall insects will not deposit eggs in any 
plant, but select certain plant species. For example, the insect may 
prefer the leaf of white oak; or another kind of gall insect may 
select the stem of goldenrod. Various factors such as color, odor, 
condition of the outer cell layers, and perhaps other things, in- 
fluence the insect to seek the plant best suited to egg-laying and 
the grub-developing part of its life. 

In plant tissues the cells adjoin each other; thus it is possible 
for dissolved substances contained in one cell to pass through cell 
walls and membranes of other cells. The membrane lining the in- 
terior of a cell controls the ease or difficulty the materials in solu- 
tion have in passing from one cell to another. This is important 
since we must consider the parts played by both the gall insect 
secretions plus the reaction of such compounds with the contents 
of living plant cells. As the insect deposits an egg in rapidly grow- 
ing parts of a plant, it may inject some of its own body fluids at 
the same time. Experimental studies have shown that a fluid of 
glandular origin is injected into the hole or wound made by the 
insect's ovipositor as the egg is pushed through. The stimulating 
fluid introduced by the insect brings about a rapid, and abnormal, 
division and growth of plant cells in the immediate vicinity of the 
insect egg. This egg, as it "hatches" and continues developing into 
a larva, also secretes fluids from its body cells. Thus the plant 
tissue in the area surrounding the egg, and finally the developing 
larva, becomes by cell division and growth distorted into a char- 
acteristic gall. The plant cells making up the gall continue growth 
which ceases when the larva inside has completed its feeding. After 
the larval stage the less active pupa develops, and finally the adult 
insect is ready to leave the gall. The shape, size, and form of the 
gall is determined not only by the gall insect, but also by the plant 
selected by that insect for its egg laying. 

It was once believed that the mechanical disturbance or injury 
caused by the insect breaking the plant tissues or by the motion 
stimulus of a growing larva on the plant cells started formation of 
a gall. At present this idea is not accepted and most investigators 
have found that chemical compounds contained in secretions of the 
adult insect and the living grub excite increased growth of plant 
cells and bring about gall formation. 

Examination will actually show that a gall is made up of plant 
tissue. An old gall may have a fibrous or spongy interior with one 
or more larval chambers embedded within it. Exit holes, from which 
the adult gall insect emerged, can be seen in many galls. These exit 
holes are known to have been prepared, in most cases, by the larva 
chewing its way to the surface before it pupates. The exit hole and 
tunnel are temporarily closed by the larva until, after completing 
pupation, it becomes a young adult and is ready to leave the gall, 
(Figs. 5, 6, 7, and 8). It can be seen from the above discussion 


that galls represent a complex relationship between plant and insect, 
but at the same time a strange biological association. It cannot be 
said that there are mutual benefits to both plant and the insect 
which produced the gall. The insect evidently benefits at the ex- 
pense of the host plant. 

To give some idea of tlie number and variety of plants visited 
by insect gall makers, E. P. Felt has listed eighty plant families 
which are known to include species which develop galls as a result 
of insect visitation. Ferns, sedges, rushes, as well as grasses, roses,, mints, and sunflowers are some of the families of plants 
where galls may be found. In the large Sunflower Family galls are 
often found on goldenrod, aster, ironweed, blazing star, and various 
species of sunflowers themselves. In Illinois some willows, hack- 
berries, hickories, walnuts, poplars and oaks are often host plants 
for a variety of galls. Among the oaks, especially, a rich representa- 
tion of gall forms may be found on catkins, acorns, leaves, twigs, 
and even roots. 

This section on plants should not be closed without some com- 
ment regarding plant malformations which have been caused by 
agents other than gall insects. Many gall-like growths, not brought 
about by gall insects at least directly, are often found on plants. 
Abnormal growth, caused by mechanical injury to stem and tree 
trunk, may result when they are girdled by cutting away bark and 
outer layers, or by binding with wire or rope. The binding and 
girdling damages conducting tissues located in the outer layer of 
woody stems just under the bark. Damage or interruption of func- 
tion of the cells and tissues results in enlarged, gall-like growth, 
and finally in death of the plant. Burls, large woody growths, from 
which burlwood veneer is made, are often found on various species 
of trees, (Figs. 65 and 66). Cedar "apples" develop from a fungus 
which in turn causes the knotty growth or "apples" common on red 
cedar. These growths, are galls but they are not insect galls, (Fig. 
64). The swollen, distorted appearance of some plants after being 
sprayed with chemical weed killers may assume gall-like form. All 
of these above malformations are not insect-caused galls in the sense 
in which we have used the term in this booklet. 


At the present time galls are of less importance as a source of 
comm.ercial products than they were several hundred years ago. 
Man once used many things produced naturally which modern 
chemical and biological laboratories now supply with more con- 
venience and less expense. 

One of the galls mentioned in ancient writings is the Aleppo 
Gall, Cynips gallae-tinctoriae, found on species of oak in Asia and 
Europe. The Aleppo Gall contained about 65 percent tannic acid 
which made it valuable in the production of astringent preparations 
used in treatment of burns, mouth infections and toothache. The 
Morea Gall, which is found on the European oak Quercus cerris L., 
was used to adulterate Aleppo Galls as a source of tannic acid em- 


ployed in tanning and dyeing processes. Ink made from some galls 
was a permanent writing fluid used at a time when most govern- 
ment records were kept as written accounts and not on punched 
cards as in modern record systems. 

Chickens, turkeys, cattle, hogs, and sheep, in some parts of the 
United States, use the deciduous black oak gall, Dryocosmos de- 
ciduous, as food. The little galls resemble dark grains of wheat. 
Birds have an interest in galls because of the grubs contained inside. 
Damaged exit holes often seen in old galls are the work of birds, 
notably woodpeckers. Mice and squirrels are known to visit galls 
possibly for the purpose of using as food the nutritive vegetable 
matter of the gall itself as well as the grub or insect inside. Galls 
are frequently found with quantities of sweet honeydew which at- 
tracts large numbers of ants, bees, wasps, and flies. Honeybees are 
known to visit galls evidently for the purpose of securing the sticky 
liquid which they finally convert into honey. Beekeepers consider 
galls an important source of potential honey. A use of gall grubs, 
not commonly known in many parts of the country, is made by ice 
fishermen who find them available in winter when other natural 
bait is scarce. 


In general the damage done to plants by the presence of galls 
is principally that of disfiguration. The gall-producing insects such 
as midges, gall-flies and mites cause considerable damage to com- 
mercial crops because of abnormal growths which these insects 
initiate on various parts of the crop plants. Fruit growers, and those 
who deal with floricultural crops, are no doubt acquainted with pear- 
leaf blister mites, apple leaf midges, and rose and chrysanthemum 
midges. These insects cause considerable damage to commercial 
crops. Trees, as well as shrubs, annual and perennial plants, and 
evergreen conebearers are all subject to damage by galls. Norway 
spruce may become infested with cone galls which are the work of 
the spruce gall aphid, and Colorado blue spruce is often disfigured 
with a similar gall. 

Galls may become abundant to the extent that they interfere 
with normal functioning of green leaves in the process of food manu- 
facture or photosynthesis. At the same time flowers and fruit fail 
to develop normally as a result. Woody galls often found on hick- 
ories and oaks may persist for years becoming unsightly and de- 
tracting from the beauty and usefulness of ornamental trees and 
shrubs. The witches' broom often seen on American hackberry, 
(Fig. 63), is probably caused by a gall mite plus a powdery mildew 
fungus. This "broom" causes twig distortions which disfigure the 
trees, and the bunching of twigs may interfere with normal produc- 
tion and distribution of leaves. Use of modern insecticides and crop 
rotation have done much to diminish losses caused by galls and gall 



If you wish to study galls and gall insects as well as collect 
specimens, it is not necessary to have elaborate equipment. Patience 
and care are as important as the materials you may use. Observa- 
tion of the gall insects will require a microscope or at least a very 
good hand lens. A reference book with keys for identification such 
as PLANT GALLS AND GALL MAKERS by E. P. Felt will be helpful and 

Dry. woody galls will present no problem in collecting and they 
can be stored in any suitable small boxes. In the case of delicate 
or soft galls it may be necessary to preserve these in small glass 
containers with some liquid preservative such as a weak formalin 
or a 50 percent alcohol solution. It is always desirable to record 
the kind of plant on which the gall was found, or to collect enough 
of the host plant for later identification. Labels giving the date and 
collection locality will make the specimens more useful to both col- 
lector and those who may want to study the galls and insects later. 
By keeping records of observations it is possible to add to the in- 
formation presently available concerning galls and gall insects. 

For the purpose of studying and observing the gall insects them- 
selves, it is best to collect the galls just prior to the time the adult 
insect will emerge. It is fairly easy to secure the freshly formed 
galls in early spring and summer. These galls can be placed in a 
large glass jar or plastic container with a cloth-covered opening for 
air. The plant stem must be placed in a small container of water 
for the plant must be kept alive if the galls and insects are to survive. 
A large, wide-mouth jar can be a good cage if the top is covered 
with cloth to admit air and at the same time the cloth prevents 
escape of the insects. Light wood frames can be covered with plastic 
to furnish cages for rearing and observing galls and gall insects. 
This method may not always be satisfactory if galls are collected 
in the autumn for at that time of year it is advisable to keep them 
over winter in jars or cages under conditions which are similar to 
those out-of-doors. A source of moisture will be needed within jars 
or cages and since some gall insects pupate in soil it will be neces- 
sary to sterilize a small amount of soil to be used in the jar or cage. 
The soil can be kept moist but not wet. Most amateur collectors 
will be sufficiently rewarded by watching the emergence of adults 
and in observing these fragile and interesting insects. The value of 
your work and your personal satisfaction will be far greater if you 
can succeed in describing a complete life cycle of a gall insect through 
all of its varied stages. 






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Fig. 7 (above). This gallfly has just emerged from a gall. The body 

appears as a moist and somewhat bedraggled individual. The folded v/ings will 

soon become dry and inflated as the fly pulsates and moves legs, wings, and 
entire body. (GSS) 

Fig. 8 (below). The gallfly's spread wings are now dry. This tiny insect 
has a wing spread of less than half an inch. The wings are marked with brown 
and these same wings will soon carry the insect to other gallflies and golden- 
rods. (GSS) 


Fig. 9 (above). Wool Sower Gall 

Gall Wasp (Callirhytis seminator Harris) 

White Oak (Quercus alba L.) 

A showy and attractive gall growth on oak twigs. The large number of 

small, hairy galls are attached to a common point to form this pinkish-white, 

wooly growth. A gall with a similar appearance may be found on several other 

species of oak. The Wool Sower was called by E. P. Felt ". . . one of the 

finest of natural objects." (CH) 

Fig. 10 (below). Oak Hedgehog Gall 

Gall Wasp {Acraspis erinacei Beutm.) 

White Oak {Quercus alba L.) 

Oak leaf galls are often observed since species of oak are favorite hosts of 

gall wasps. The Acraspis Galls are complicated because of the sexual and 

agamic forms (See Fig. 3 and discussion of alternation of generations). These 

reddish-green Hedgehog Galls are the agamic form and may be spiny or nearly 

smooth. (CH) 


Fig. 11 (above). Oak Potato Gall 

Gall Wasp (Callirhytis seminosa Bass.) 

Pin Oak (Quercus palustris Muench.) 

Hard, woody knots mark the appearance of this gall on twigs of pin oak, 

and they are sometimes described as resembling a strawberry. These galls have 

been cut lengthwise to show the interior structure and the larval cells. (KB) 

Fig. 12 (below). Oak Pill Gall 
Gall Midge (Cincticornia pilulae Walsh) 
Shingle Oak (Quercus imbricaria Michx.) 
These Pill Galls are rounded and sometimes nearly globular in form. They 
appear as dark red growths on the upper side of the shingle oak leaf. There 
are many kinds of Pill Galls and some of them are found only on the underside 
of the leaves. (CH) 


Fig. 13 (above). Small Oak Apple 

Gall Wasp (Andricus singularis Bass.) 
Red Oak (Quercus rubra L.) 
In autumn it is easy to find the Small Oak Apple on fallen oak leaves. The 
photograph shows opened galls with slender fibers which support the larval cell 
inside near the center. In diameter this oak apple is about one inch, and while 
young it is light green. Later in summer it will become thin walled, brittle and 
brown. (KB) 

Fig. 14 (below). Bassett's Oak Gall 

Gall Wasp (Disholcaspis bassetti Gill.) 

Shingle Oak (Quercus imbricaria Michx.) 

The flask-shaped galls are light green and hairy in early summer. Later 

they will become brown like the twig from which they developed. Bassett's Oak 

Gall is found as a single or clustered growth. (CH) 


Fig. 15 (above). Black Oak Gall 

Gall Midge (Cecidomyia Sp.) 

Black Oak (Quercus velutina Lam.) 

Since the species of fly-like midge which is responsible for this gall is not 

known, it will serve to show how much work is needed in the study of galls 

and gall insects. These dark brown galls are found on the underside of the 

black oak leaf very near the main veins. (CH) 

Fig. 16 (below). Rough Bullet Gall 

Gall Wasp (Disholcaspis mamma Cresson) 

Swamp White Oak (Quercus bicolor Willd.) 

These round, nipple-tipped galls are found on several species of oaks. They 

are colored green and red when young, velvety to touch, later becoming red 

or dark brown. In winter the galls are very hard and may be cut with difficulty. 

Rough Bullet Galls are generally found on young shoots of oak. (CH) 


Fig. 17 (above). Marbled Oak Gall 

Gall Wasp (Andricus pisiiormis Beutm.) 

White Oak (Quercus alba L.) 

A small oak gall, found in spring, white or pale green often mottled with 

darker colors. Mabled Oak Galls, which develop from buds, are fleshy at first 

later becoming dry and hollow. (KB) 

Fig. 18 (below). Oak Rosette Gall 

Gall Wasp (Andricus foliosus Weld) 

Swamp White Oak (Quercus bicolof Willd.) 

Fleshy green segments of modified leaves enclose this gall which occurs on 

the upper surface of leaves of young oaks and oak sprouts. Several larval cells 

may be found inside each gall. (CH) 


Fig. 19 (above). Oak Bullet Gall 

Gall Wasp (Disholcaspis quercus-globulus Fitch) 

White Oak (Quercus alba L.) 

Oak Bullet Galls are single or clustered; however they do not have the 

beaked structure found in the Rough Bullet Gall. These bullet galls may be 

about two-thirds of an inch in diameter on various species of the white oak 

group. Freshly formed galls are generally yellowish-red and are often collected 

from fallen twigs. An exit hole is plainly visible in the uppermost gall on the 

right. (CH) 

Fig. 20 (below). Oak Bullet Gall 
Gall Wasp (Disholcaspis quercus-globulus Fitch) 
White Oak (Quercus alba L.) 
These oak galls are about three quarters of an inch in diameter and occur 
singly or sometimes in clusters. The color of the freshly formed galls is yellow- 
ish-red and, later in summer, dark red or brown. (CH) 


Fig. 21 (above). Oak Bullet Gall 

Gall Wasp (Disholcaspis quercus- globulus Fitch) 

White Oak (Quercus alba L.) 

A section cut through the middle of an Oak Bullet Gall. The spongy, fibrous 
interior of the gall can be seen as well as the larval cell in the center on the 
right. The scale is in centimeters. (KB) 

Fig. 22 (below). Woody Twig Gall 

Gall Wasp {Callirhytis tuberosa Bass.) 
Shingle Oak {Quercus imbricaria Michx.) 

Sometimes every twig on a shingle oak may be distorted by this dark 
brown, woody gall. It is a many-celled growth and has a warty, potato-like 
appearance. (CH) 









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Fig. 25 (above). Oak Wool Gall 

Gall Wasp (Andricus flocci Walsh) 

Shingle Oak (Quercus imbricaria Michx.) 

There are many wool galls of different shapes, sizes and color. This gall 

is grayish-cream when fresh and it is difficult to find except on low growing 

branches or when twigs or leaves have fallen to the ground. (CH) 

Fig. 26 (below). Spiny Rose Gall 

Gall Wasp (Diplolepis bicolor Harris) 

Pasture Rose (Rosa Carolina L.) 

The hollow green and red galls seem to imitate the spiny condition of the 

host plant. The genus of wasps which produces this gall in spring is so closely 

associated with the Pasture Rose that the galls are not likely to be found on 

any other plants. Spiny Rose Galls occur singly or in groups which turn brown 

;iid may lose the spines as they become older. (CH) 


Fig. 2 7 (above). Cinquefoil Axil Gall 
Gall Wasp (Gonaspis potentillae Bass.) 
Common Cinquefoil (Potentilla simplex Michx.) 
The Cinquefoil Axil Gall is green and sparsely hairy in its early develop- 
ment and will turn brown later in summer. Note clusters of modified leaves 
which are part of the gall itself. This gall is not often found although com- 
mon cinquefoil is a plant bearing small yellow flowers frequently seen in woods 
and along roadsides. (CH) 

Fig. 28 (below). Blackberry Seed Gall 
Gall Wasp (Diastrophus cuscutaeformis O. S.) 
Blackberry (Rubus allegheniensis Porter) 
In this "Seed Gall" the cluster is made up of individual galls each of which 
is hairy and spined near the tip. Note that the spiny growth of the gall simu- 
lates the spiny cane of the blackberry. This particular gall is not common 
although the blackberries and raspberries are frequent hosts for a number of 

gall insects. (KB) 


Fig. 29 (above). Blackberry Knot Gall 
Gall Wasp (Diastrophus nebulosus O. S.) 
Blackberry (Rubus allegheniensis Porter) 

This is a long, stem swelling with a warty appearance. There are generally 
a number of deep furrows present in the dark brown or purplish gall which 
may be three inches in length. Some observers maintain that the galls are 
more likely to be found on plants growing in slightly acid, sandy soil. It is 
possible that the adult wasp selects these plants in preference to those grow- 
ing in other kinds of soil. (CH) 

Fig. 30 (below). Blackberry Knot Gall 
Gall Wasp (Diastrophus nebulosus O. S.) 
Blackberry (Rubus allegheniensis Porter) 
A lengthwise cut through a Blackberry Knot Gall to reveal a number of 
larval chambers embedded in the porous, woody tissue of the gall. (KB) 


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Fig. 33 (above). Poplar Stem Gall 

Aphid {Pemphigus populicaulis Fitch) 

Cottonwood {Populus deltoides Marsh.) 

Another common gall found on cottonwood leaves where it is located near 

the base of the leaf or blade. Newly formed galls are reddish-green when young 

and then turn darker with age. The opening in the gall is a characteristic, 

elongated slit and the interior of the gall is inhabited by aphids or plant lice. 

Hundreds of leaves from one tree may bear these galls. (CH) 

Fig. 34 (belov/). Poplar Petiole Gall 

Aphid (Pemphigus populitransversus Riley) 

Cottonwood (Populus deltiodes Marsh.) 

In contrast with the Poplar Stem Gall this growth appears near the middle 

of the petiole or leaf stem. This is a photograph of an old gall which is hollow 

but when fresh would be found to contain plant lice. (CH) 


Fig. 35 (above). Vagabond Poplar Gall 

Aphid (Mordwilkoja vagabunda Walsh) 

Cottonwood {Populus deltoides Marsh.) 

A very apparent deformity of cottonwoods. The gall is said to be found 

on trees which stand in water part of the time, or on young trees. Plant lice, 

which stimulate the formation of the gall, attack leaf buds in early spring 

transforming them into lobed, irregular, hollow masses in which many aphids 

may be found. The galls, green at first, become dark brown or black. (CH) 

Fig. 36 (below). Vagabond Poplar Gall 

Aphid (Mordwilkoja vagabunda Walsh) 

Cottonwood (Populus deltoides Marsh.) 
An enlarged view of the gall. The growth is not heavy and woody as the 
photograph might indicate, but spongy and hollow since it originates from young 
leaves. This gall was a little less than two inches across at its widest pomt. (CH) 


Fig. 37 (above). V/illow Cabbage Gall 

Gall Midge (Rhabdophaga brassicoides Walsh) 

Willow (Salix humilis Marsh.) 

An open, rosette gall found in spring and early summer on shrubby 

willows. The loose, leafy and bract-like parts of the gall resemble shortened 

l^^aves of the willow. This gall is rather hairy and gray-green in color. (CH) 

Fig. 38 (below). Willow Cabbage Gall 
Gall Midge (Rhabdophaga brassicoides Walsh) 
V/illow (Salix Sp.) 
An old Willow Cabbage Gall in winter condition. The growth developed, 
from a bud and formed a gall which has a loose appearance rather than the.- 
closely-overlapping parts of the Pine Cone Willow Gall. (KB) 


Fig. 39 (above). Pine Cone Willow Gall 
Gall Midge (Rhabdophaga strobiloides Walsh) 
Willow (Sallx Sp.) 
The overlapping, scale-like growths of this gall seem to resemble the seed- 
bearing cones of pine trees. Separate parts of the gall, which have a gray- 
green, velvety appearance, look like the leafy bracts which one might find be- 
low a flower. The host plant is generally one of the shrubby species of wil- 
low. (CH) 

Fig. 40 (below). Pine Cone Willow Gall 

Gall Midge (Rhabdophaga strobiloides Walsh) 

Willow (Salix Sp.) 

A section cut through two Pine Cone Willow Galls. The fibrous structure 
of the interior of the gall is apparent as well as the cone-like, overlapping 
"scales". The larval chamber is near the center of the gall. (KB) 


Fig. 41 (above). Pine Cone Willow Gall 

Gall Midge (Rhabdophaga strobiloides Walsh) 

Willow (Salix humilis Marsh.) 

This specimen has been identified with the same name as the smooth-tippeo 

gall in Fig. 39. Notice that scale-like bracts have tufts very unlike those of 

the smooth-tipped Pine Cone Gall. Later during the summer these pale green, 

velvety gall growths will turn brown. (CH) 

Fig. 42 (below). Willow Knot Gall 

Sawfiy (Euura propinqua Rohw.) 

Willow (Salix Sp.) 

An abrupt swelling on willow twigs or small branches characterizes this 

rather uncommon gall. Its warty appearance resembles, in miniature, the very 

large gall-like growths sometimes seen on tree trunks. The sawfiy responsible 

for the gall is not a true fly but belongs with the bees and wasps. (KB) 


Fig. 43 (above). Poplar Twig Gall 
Gall Fly (Agromyza schineri Giraud.) 
Quaking Aspen {Populus tremuloides Michx.) 
Although quaking aspen belongs with the Poplars, it is a more common tree 
in north central Illinois. The gall is a rather irregular, oval swelhng on srnaller 
twigs. The gray-green color of these twig galls resembles that of the 
themselves. Note that the new, leafy shoots appear to grow 
itself. (KB) 

Fig. 44 (below). Leaf Roll of Elm 
Aphid (Georgiaphis ulmi Wilson) 
Slippery Elm (Ulmus rubra Muhl.) 
unlike the Cockscomb Gall on American elm, 

of the slippery elm leaf. The coarse, rough leaves 

and roll as the gall develops. Aphids or plant hce are often 

gall. The presence of these aphids is a biological characteristic which actually 
helps to identify the tree. (CH) 


This gall, 

through the gall 

is found on the 
of the elm curl 
found inside the 

Fig. 45 (above). Elm Bud Gall 

Gall Midge {Dasyneura ulmea Felt) 

Slippery Elm (Ulmits rubra Muhl.) 

The slippery elm has large, hairy, reddish buds in which the fly-like midge 

deposits eggs. The galls are made up of a very large number of bud scales and 

immature leaves in early spring. The Elm Family, which includes hackberries 

as well as elms, is noteworthy for many galls and gall insects. (KB) 

Fig. 46 (below). Cockscomb Elm Gall 

Aphid (Colopha ulmicola Fitch) 
American Elm (Ulmus americana L.) 
A green and red gall found on the upper side of American elm leaves and 
named from its fancied resemblance to a rooster's comb. The ridged growths 
appear between leaf veins, and the gall will contain aphids responsible for its 
formation. Cockscomb Elm Gall is likely to be found on young trees and those 
subject to flooding in the early part of summer. (CH) 


Fig. 47 (above). Pouch Gall of Sumac 

Gall Mite (Eriophyes Sp.) 
Fragrant Sumac (Rhus aromatica Ait.) 
Some of the sumacs, which include poison ivy and poison sumac, may be 
toxic to man but they support a number of gall mites and midges. The sumac 
leaf shown is from one of the harmless kinds often found as a low shrub m 
Illinois. The mites v^^hich produce the reddish pouch or cylindrical galls are m- 
dividually smaller than the head of a pin. (CH) 

Fig. 48 (below). Nettle Bud Gall 

Gall Midge (Cecidomyia Sp.) 

Wood Nettle {Laportea canadensis (L.) Gaud.) 

The tiny insect which visits this wood nettle is evidently not distracted by 

the stimulus of stinging hairs of the plant. Anyone who has walked in wet 

woodlands in summer is likely to see, not only the galls, but make contact with 

the stinging hairs of wood nettle. These greenish, irregular growths appear m 

early summer and the midges are fly-like insects. (CH) 


Fig. 49 (above). Grape Phylloxera 
Aphid (Phylloxera vitifoliae Fitch) 
Frost Grape (Vitis vulpina L.) 
The Phylloxera Galls of wild grape are often abundant to the point of dis- 
torting the individual leaves noticeably. These galls are the work of plant 
lice or aphids and they occur on the under side of the leaves. Virginia Creeper 
or Woodbine, of the same plant family, is often a host for similar galls. (CH) 

Fig. 50 (below). Grape Filbert Gall 

Gall Midge {Schizomyia coryloides Walsh 8e Riley) 

Wild Grape (Vitis Sp.) 

An uncommon, clustered gall which takes its name from a similar shape 

of the filbert. These hairy, green bud galls apparently develop from leaf buds 

since they appear opposite the tendril on the grape twig. Grape flowers may 

also develop from the same position on the twig. (KB) 



Fig. 53 (above). Goldenrod Ball Gall 

Gall Fly (Eurosta soHdaginis Fitch) 

Goldenrod (Solidago altissima L.) 

A globular stem gall whose interior is filled with plant tissue in which a 

larval cell is embedded. Although common, this gall is probably less likely to 

be seen than the Goldenrod Bunch Gall. Since the stem has continued its growth 

the gall fly apparently deposits an egg in the stem tissue below the growing 

tip. (CH) 

Fig. 54 (below). Goldenrod Ball Gall 

Gall Fly (Eurosta solidaginis Fitch) 

Goldenrod (Solidago altissima L.) 

The galls are about one inch in diameter with a hard, pithy interior in 

which a larval chamber occurs. It is the larvae found in these galls which are 

reportedly used by ice fishermen. Late in summer the galls become light brown 

and have the same appearance as the goldenrod stem. (KB) 


Fig. 55 (above). Goldenrod Bunch Gall 
Gall Midge (Rhopalomyia solidaginis Lw.) 
Goldenrod {Solidago altissima L.) 
A Goldenrod Bunch Gall as it appears at the growing tip of a main shoot 
of the plant. In this stage the lateral or side branches have not yet developed. 
The gall gives the appearance of leaves clustered at the tip instead of being 
distributed along the normal length of the stem. The cell of the midge larva 
is in the center of the cluster of shortened, deformed leaves. (CH) 

Fig. 56 (below). Goldenrod Bunch Gall 
Gall Midge (Rhopalomyia solidaginis Lw.) 
Goldenrod (Solidago altissima L.) 
An old Bunch Gall which makes its appearance in autumn. Note the de- 
velopment of many lateral or side branches which may be the result of mter- 
ference with growth of the terminal bud. In autumn this gall may be found m 
patches of goldenrod. (CH) 


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Fig. 59 (above). Apical Stem Gall of Cup Plant 

Gall Wasp (Antistrophus silphii Gill) 
Cup Plant (Silphium perioliatum L.) 
This rather uncommon gall appears at the tip of a growing stem of Cup 
Plant. It is green and often irregular in shape. The gall growth strongly re- 
sembles an unopened flower bud. (KB) 

Fig. 60 (below). Apical Stem Gall of Cup Plant 
Gall Wasp (Antistrophus silphii Gill) 
Cup Plant (Silphium perfoliatum L.) 
A cut has been made lengthwise through the galls to show numerous larval 
chambers and some of the grubs. (KB) 



Fig. 63 (above). Witches' Broom on Hackberry 

Gall Mite (Aceria snetsingeri Keifer) 

Fungus (Sphaerotheca phytoptophyla) 

Hackberry (Celtis Occident alls L.) 

The "brooms" of hackberry trees (Celtis occidentalis L.) result from dwarfed 

and clustered buds. The twigs are shortened and bunched due to the presence 

of two agents: a powdery mildew and a gall mite. (JG and CH) 

Fig. 64 (below). Cedar "Apples" on Red Cedar 
This is not an insect-produced gall but the cedar "apple" rust stage of the 
fungus Gymnosporangium juniperi-virginiana. The disease requires two hosts, 
the other being redhaw (hawthorn) or cultivated apples and their relatives. On 
wet days in spring these cedar "apples" will develop yellow, horn-like, gelatmous 
protuberances which in turn bear spores carried by wind to leaves of redhaw 
and apple. Yellow-orange spots appear on the leaves and the fungus producmg 
them is Gymnosporangium globosum. The spores of this fungus again mfect 
red cedar to continue the cycle. (JG) 


Fig. 65 (above). Tumor of Elm 

A gall or plant tumor on the trunk of an elm. The twisted, contorted grain 
of these woody galls is known as "burl" and the finished wood or veneer from 
such a source is often beautiful and decorative. It may be that such a growth 
involves a bacterium or even a virus. (JG) 

Fig. 66 (below). Tumor of Pin Oak 

Plant galls may be regarded as tumors since they represent abnormal growth 
of plant cells. The photograph shows a large gall or tumor on the trunk of 
pin oak (Quercus palustris Muench.). The swollen, deformed trunk of the oak 
is obvious, but such a growth may be caused by a combination of several agents 
including insects, fungi, and mechanical injury. (JG) 


Fig. 67. Three Galls on Hackberry 

This single leaf of hackberry {Celtis occidentalis L.) is a host for three 
distinct galls. (A) Spiny Hackberry Gall (Cecidoznyia spiniiormis Patton). The 
insect stimulating the formation of this growth is a gall midge. (B) Hackberry 
Nipple Gall (Pachypsylla celtidismamma Riley). This gall insect and the fol- 
lowing are both jumping plant lice. These lice are not the same as plant lice 
or aphids. The galls appear in summer after the leaves are grown, but they are 
not confined to any particular part of the leaf. (C) Hackberry Blister Gall 
(Pachypsylla vesiculum Riley). These small galls may pass unnoticed but care- 
ful observation will reveal them on many hackberry leaves. (Photo Courtesy 
of Illinois Natural History Survey, Wm. E. Clark) 




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English, L. L. . 

1958 lUinois trees and shrubs: their insect enemies. Illinois Natural His- 
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Fagan, Margaret 

1918 The uses of insect galls. Amer. Nat. 52: 155-176. 

Fischer, Richard B. 

1958 The curious world of plant galls. Audubon Mag. Nov.-Dec. 264- 


Gronemann, C. F. -r^. , , ,>, * 

1930 Fifty common plant galls of the Chicago area. Field Museum of 
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Hovanitz, William . ,r , o«, t^t e 

1959 Insects and plant galls. Scientific American. Nov. Vol. 201, No. by 

151 ff. 

Lutz, Frank E. , r. ^-r -.z i 

1935 A field book of insects. 3rd ed. G.P. Putnam's Sons. New York. 

Pittman, H. H. 

1938 Prairie galls. Nature Magazine, Jan. 51: 24. 

Smith, Gordon S. 

1957 Nature's doorless house. Nature Magazine, Dec. 50: 532-33. 

Wright, Gilbert A. . 

1951 Common Illinois insects. Story of Illinois No. 8, Illinois State Mu- 
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Ballow, L. M. ^ ,., . ^ i T- . -7 1 

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Kinsey, A. C. 

1930 The gall wasp genus Cynips. Indiana University Studies. Vol. 16. 
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1936 The origin of higher categories in Cynips. Indiana University Sci- 
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Lienk, Siegfried E. 

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192 7 Cynipid galls of the Chicago area. Illinois State Acad, of Sci. Trans. 
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1937 Phytohormones. Macmillan Co., New York. 


• 'i 


Aceria snetsingeri, 45 

Acraspis erinacei, 18 

Agromyza schlneri, 35 

Alteration of generations, explanation 

(drawing), 9 
Andricus flocci, 26 

toliosus, 22 

pisiformis, 22 

singularis, 20 
Antistrophus silphii, 43 
Aphid, 30, 31, 35, 36, 38 
Aphid nymph (drawing), 7 
Aphid, winged adult (drawing), 7 
Asphondylia ceanothi, 39 

helianthi florae, 44 
Aulacidea tumida, 42 
Axil gall, cinquefoil, 27 

Ball gall, goldenrod. 39, 40 
Bassett's gall, oak, 20 
Black oak gall, 21 
Blackberry, 2 7, 28 
Blackberry knot gall, 28 
Blackberry seed gall, 2 7 
Blister gall, hackberry, 47 
Bud gall, elm, 36 
Bud gall, nettle, 37 
Bullet gall, oak, 23, 24 
Bullet gall, rough, 21 
Bunch gall, goldenrod, 41 

Cabbage gall, willow, 32 
Callirhytis seminator, 18 

seminosa , 1 9 

tuberosa, 24 
Gary a illinoensis, 29 
Caryotnyia holotricha, 29 
Ceanothus americanus, 39 
Cecidomyid larva (drawing), 8 
Cecidomyia sp., 21, 37 

spiniformis, 47 

thurstoni, 44 
Cedar "apples", 45 
Cedar, red, 45 
Celtis occidentalis, 45, 47 
Cincticornia pilulae, 19 
Cinquefoil axil gall, 2 7 
Cinquefoil, common, 27 
Cockscomb gall, elm, 35 
Colopha ulmicola, 36 
Colopha ulmicola (drawing), 7 
Cottonwood, 30, 31 
Crataegus mollis, 29 
Cup plant, 43 
Cup plant, apical stem gall, 43 

Dasyneura ulmea, 36 
Diastrophus cuscutaeiormis, 2 7 

nebulosus, 28 
Diplolepis bicolor, 26 
Disholcaspis bassetti, 20 

mamma, 21 

quercus- globulus, 23, 24 

Elliptical gall, goldenrod, 42 

Elm, american, 36 

Elm bud gall, 36 

Elm. cockscomb gall, 36 

Elm, leaf roll, 35 

Elm, slippery, 35, 36 

Elm, tumor, 46 

Eriophyes pyri (drawing), 7 

Eriophyes sp., 37 

Eurosta solidaginis, 16, 39, 40 

Euura propinqua, 34 

Filbert gall, grape, 38 
Flower heads, abnormal. 
Fungus, 45 


Gall fly, 16, 17, 35, 39, 40 

Gall formation (drawing), 11 

Gall gnat, male (drawing), 7 

Gall midge, 19, 21, 29, 32-34, 36-39, 

41, 44 
Gall mite, 37, 45 
Gall moth, 42 

Gall producing insects (drawing), 7 
Gall wacp, 18-28, 42, 43 
Gall wasp, female Cynips (drawing), 7 
GeoTgiaphis ulmi, 35 
Gnorimoschema gallae-solidaginis, 42 
Goldenrod, 39-42 
Goldenrod ball gall, 39, 40 
Goldenrod bunch gall, 41 
Goldenrod gall, elliptical, 42 
Gonaspis potentillae, 2 7 
Gouty oak gall, 25 
Grape filbert gall, 38 
Grape, frost, 38 
Grape phylloxera, 38 
Grape, wild, 38 

Gymnosporangium globosum, 45 
Gymnosporagnium juniperi-virginiana, 


Hackberry, 45, 47 
Hackberry blister gall, 47 
Hackberry nipple gall, 47 
Hackberry gall, spiny, 47 
Hedgehog gall, oak, 18 

'■■' From photographs unless otherwise noted. 


Helianthus grosseserratus, 44 

Helianthus, sp., 44 

Hickory, 29 

Hickory onion gall, 29 • \ 7 

Hormosomyia oregonensis (drawing;, / 

Knot gall, blackberry, 28 
Knot gall, willow, 34 

Lactuca sp., 42 

Laportea canadensis, 37 

Leaf roll of elm, 35 

Lettuce tumor gall, 42 

Lettuce, wild, 42 

Lice, jumping plant, 47 . x 7 

Louse, jumping plant (drawmg), 7 

Marbled oak gall, 22 

Mite, pear-leaf blister (drawing), 7 

Mordwilkoja vagabunda, 31 

Nettle bud gall, 37 
New Jersey tea, 39 
Nipple gall, hackberry, 47 

Oak apple, small, 20 
Oak bullet gall, 23, 24 
Oak gall, Bassett's, 20 
Oak, black, 21 
Oak gall, black, 21 
Oak gall, gouty, 25 
Oak hedgehog gall, 18 
Oak gall, marbled, 22 
Oak pill gall, 19 
Oak, pin, 19, 46 
tumor of, 46 

Oak potato gall, 19 

Oak, red, 20 

Oak rosette gall, 22 

Oak, shingle, 19, 20, 24-26 

Oak, swamp white, 21, 22 

Oak white, 18, 22, 23, 24 

Oak wool gall, 26 

Onion gall, hickory, 29 

Pachypsylla celtidismamma, 47 
celtidismamma (drawing), 7 
vesiculum, 47 

Pemphigus populicaulis, 30 
populitransversus, 30 

Petiole gall, poplar, 30 

Phylloxera vitiioliae, 38 

Pill gall, oak, 19 

Pine cone willow gall, 33, 34 

Plagiotrochus punctatus, 25 

Poplar petiole gall, 30 

Poplar stem gall, 30 

Poplar twig gall, 35 

Potato gall, oak, 19 

Pouch gall, sumac, 37 

Poplar gall, vagabond, 31 

Populus deltoides. 30, 31 
tremuloides, 35 

Potentilla simplex. 2 7 

Quaking aspen, 35 

Quercus alba, 18, 22, 23, 24 

bicolor, 21, 22 

imbricaria, 19, 24-26 

palustris. 19, 46 

rubra, 20 

velutina, 21 

Red haw, 29 
Redroot bud gall, 39 
Rhabdophaga brassicoides, 32 

strobiloides, 33, 34 
Rhopalomyia solidaginis, 41 
Rhus aromatica, 37 
Rosa Carolina, 26 
Rose, pasture, 26 
Rose gall, spiny, 26 
Rosette gall, oak, 22 
Rough bullet gall, 21 
Rubus allegheniensis, 27, 28 

Salix humilis, 32, 34 

Salix, sp., 32-34 

Sawfly, 34 

Seed gall, blackberry, 27 

Schizomyia coryloides, 38 

Silphium pertoliatum, 43 

Solidago altissima, 39, 40-42 

Sphaerotheca phytoptophyla, 45 

Spiny gall, hackberry, 47 

Spiny gall, rose, 26 . , ^^ 

Stem gall of cup plant, apical, 43 

Stem gall, poplar, 30 

Stem gall, sunflower, 44 

Sumac, fragrant, 37 

Sumac, pouch gall, 37 

Sunflower, 44 

Sunflower, sawtooth, 44 

Sunflower stem gall, 44 

Thorn cockscomb gall, 29 
Trishormomyia crataegifolia, 29 
Tumor gall, lettuce, 42 
Twig gall, poplar, 35 
Twig gall, woody, 24 

Ulmus americana, 36 
rubra, 35, 36 

Vagabond gall, poplar, 31 
Vitis, sp., 38 
Vitis vulpina, 38 

Willow, 32-34 
Willow cabbage gall, 32 
Willow gall, pine cone, 33, 
Willow knot gall, 34 
Witches' broom, 45 
Wood nettle, 37 
Woody twig gall, 24 
Wool gall, oak, 26 
Wool sower gall, 18 






507IL61ST C006 


12 1961 


3 0112 025311009