ILLINOIS HISTO'-IC^.L fJiJRVEY University of I.Viizioii; SOME Glen S. Winterri ILLINOIS STATE MUSEUM STORY OF ILLINOIS No. 12 STORY OF ILLINOIS SERIES 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 STATE OF ILLINOIS Otto Kerner, Governor DEPARTMENT OF REGISTRATION AND EDUCATION William Sylvester White, Director ILLINOIS STATE MUSEUM Thorne Deuel, Museum Director STORY OF ILLINOIS SERIES, NO. 12 SOME PLANT GALLS OF ILLINOIS by Glen S. Winterringer [Printed by authority of the State of Illinois.] 1961 BOARD OF ILLINOIS STATE MUSEUM ADVISORS M. M. Leighton, Ph.D., D. Sc, Chairman State Geological Survey, Urbana Everett P. Coleman, M.D. Coleman Clinic Canton Percival Robertson, Ph.D., LL.D. The Principia College Elsah N. W. McGee, Ph.D. North Central College Naperville Sol Tax, Ph.D., Secretary University of Chicago Chicago ^ \^ I ho . I ^ SOME PLANT GALLS OF ILLINOIS Contents PAGE 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 ACKNOWLEDGMENTS 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). INTRODUCTION 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. HISTORICAL SKETCH 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 plant. 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. GALL PRODUCERS AND HOW GALLS ARE FORMED (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". ^ ' FEMALE 2 MALE B ASEXUAL FEMALE 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, 10 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. 11 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 12 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, legum.es, 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. USES OF GALLS 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- 13 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. DAMAGE DONE BY GALLS AND GALL INSECTS 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 insects. 14 SUGGESTIONS FOR GALL STUDY AND COLLECTING 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 advisable. 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. 15 3 > (U o to CO a CO Q, CO > S > U w. ,S « (D -M , , t" _ CO ^ T3 ■^ u X t3 . CO fH CO - § Q a (O X x; •►-' . X O c 1) •4-' CO u CO ^^ CO ii o -o ■ n -^ CO -^ - o £ (L) ;:3 ' _C! t« 4_» h/l CO O O ^ bJD cs ■4-* ill C! O •o C 3 O s x: ♦J « c >- S 1) o 2 S P M X , «J ^ -^ I -2 ^- ^ • « o • .Sf 6 a.5f ^ l-[ 4-1 1^ I-" +J 3 O u bfl 25 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) 26 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) 27 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) 28 CO flJ x; J5 CO O S O o u o U c o JZ x: CO o o T3 C CD to ^^ • — u C CO =8 .i2 OH ° 2 6 S I. o tD 3 N.^ CO •o O S 0 ffl M . —I CO > CO OJ C D O a o tj U 3 M c o o a o *^ -- a G o <*-. « CO 1) ^ u CO , M O CO i en J5 Ij ■£ 29 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) 30 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) 31 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) 32 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) 33 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) 34 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) 35 This gall, underside twigs 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) 36 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) 37 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) 38 39 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) 40 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) 41 CO bx) bfl 3 o S2 u W V u CO , ^^ X x; ^ -^ +j en « tl CD u m •C ? J^ S) ■M O •o ^ C M c e e « « s « „ o CD "■ ■4-< ^ 0 u (13 •a Q. 3 u I5| o g 5 3 CO o 3 3H CA .s^: D ■w -*-l ." (U >*-. fc H to o <0 5°-2 o S fe-c 3 ;j t-. -^ .y •4-' ^ CJ ^ c »ii OJ "a 3 3 CO J ^ 4-J 4-1 |a DO 00 a x; D o VO CO 2 2 M CO ii CO S « c T3 >, ^3 T3 O w in 0. w u X 2 w X O, I-. j-< CO '4-' CO 0) M >- s O X c >> °1 CO ■» S Sii c 1) V w H CJ ^ > y "o ' r^ '— CO R CO [ft ^^ .5" t^ -^ tl -rt -^ "U s .2 '^ ■— ( ]2 ,<*^ x: o 5i o 0 ,, CO 0 O •5) CO »— - 0 J CO 1 x: o ^ flj CO "" •C X i* ■^ cft m > OJ CO x: a 5 2 c 1) 0 •2 "co V} 0 M 1) X £ ° 0 i! 0 u g •. 0 J-* U Ui V ^ CO c 42 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) 43 44 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) 45 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) 46 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) 47 REFERENCES FOR BEGINNING STUDY Carter, J. C. 1955 Illinois trees: their diseases. Illinois Natural History Survey Circular No. 46. Cook, M. T. 1905 The insect galls of Indiana. Dept. of Geol. & Nat. Resources; Annual Report. 1910 Insect galls of Michigan. Mich. Geol. 8e Biol. Survey 1: 23-33. 1923 Origin and structure of plant galls. Science, 57: 6-14. English, L. L. . 1958 lUinois trees and shrubs: their insect enemies. Illinois Natural His- tory Survey Circular No. 47. 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- 269. Gronemann, C. F. -r^. , , ,>, * 1930 Fifty common plant galls of the Chicago area. Field Museum of Natural History, Botany Leaflet 16. 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- seum, Springfield. FOR WORE ADVANCED STUDY Ballow, L. M. ^ ,., . ^ i T- . 0 -7 1 K25 Some Dipterous galls of southern Cahfornia. Jour, of Ent. Ss Zool. Clarcmont. Cal., 17: 2 5-32. T924 Galls that secrete honeydcw. Bull. Brooklyn Ent. Soc, 19: 101-124.. 48 Comstock, J. H., Comstock, A.B., and Herrick, G. W. 1931 A manual for the study of insects. 20th ed. Comstock Publishing Co., Ithaca, N.Y. Comstock, J. H. 1940 An introduction to entomology. 9th revised ed. Comstock Publishing Co., Ithaca, N.Y. Cosens, A. 1912 A contribution to the morphology and biology of insect galls. Toronto Univ. Studies, 13: 297-387. Emanuel, C. F. 1961 Rare tumor in coast redwood, Sequoia sempervirens. Science, 133: 1420-1421. Felt, E. P. 1925 Key to the gall midges. N. Y. State Museum Bull. No. 257. 1936 Gall production. Ann. Ent. Soc. America. 29: 694-700. 1940 Plant galls and gall makers. Comstock Publishing Co., Ithaca, N.Y. Kinsey, A. C. 1930 The gall wasp genus Cynips. Indiana University Studies. Vol. 16. Bloomington, Indiana. 1936 The origin of higher categories in Cynips. Indiana University Sci- ence Series No. 4. Bloomington, Indiana. Lienk, Siegfried E. 1947 A study of some gall insects. Master's thesis. University of Illinois, Urbana. Martin, J. F. 1942 Stem galls of sugar cane induced with insect extracts. Science 96: 39. Metcalf, C. L., and Flint, W. P. 1939 Destructive and useful insects. 2nd ed. McGraw-Hill Book Co., New York. Peterson, Alvah Larvae of insects. Part II. Edwards Brothers, Inc., Ann Arbor, Michigan. Pritchard, A. E. 1951 North American gall midges (Diptera). University of California. Weld, L. H. 1922 Notes on Cynipid wasps. Proc. U. S. Nat. Museum 61: 1-29. 1S26 Field notes of gall-inhabiting Cynipid wasps. Proc. U. S. Nat. Mu- seum 68: 1-131. 192 7 Cynipid galls of the Chicago area. Illinois State Acad, of Sci. Trans. 20: 142-177. Went, F. W. 1937 Phytohormones. Macmillan Co., New York. 49 • 'i ILLUSTRATIONS* 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 44 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, 45 Hackberry, 45, 47 Hackberry blister gall, 47 Hackberry nipple gall, 47 Hackberry gall, spiny, 47 Hedgehog gall, oak, 18 '■■' From photographs unless otherwise noted. 50 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 34 51 OF ILLINOIS Y, UNIVERSITY OF ILLINOIS-URBANA 507IL61ST C006 STORY OF ILLINOIS SERIES. SPRINGFIELD 12 1961 \} 3 0112 025311009