Thecabius populimonilis

Thecabius populiconduplifolius

Pemphigus populicaulis

Pemphigus populiglobuli

Pemphigus populitransversus

Pemphigus populivenae

Pemphigus populiramulorum

Pemphigus betae

Prociphilus fraxinifolii

Thecabius populi-monilis (Riley). 

This aphid forms characteristic rows of bead-like cells, particularly on the upper sides of the leaves of narrow-leaved cottonwood, Populus angustifolia, and to a less extent on some of the wider-leaved species of poplars. The stem mother produces a gall similar to that formed by her young. These galls occur singly, usually between the midrib and the margin of the leaf. The first bead-like rows of galls are produced by the young of the fundatrix. Only a single individual is found in each cell. 

According to Gillette, most of the second generation lice become winged and leave the galls, thus serving to scatter the species from tree to tree. A portion, especially of the later lice that are born, remain apterous, remain in the galls, and give rise to the third generation. These young, like the young from the stem mother, also migrate to the new leaves to continue the production of galls each of which harbors but one louse at first, but a portion of the young of this brood remain with the mother in the gall and become winged sexupara, of which 10 or 12 may be found in a single gall with the parent. Emergence of these sexupara begins about the first week of August and continues until the last of September; soon after emergence the sexupara give birth to the se.xual forms. 

On the narrow-leaved cottonwood, the galls are most commonly in rows, on one or both sides, and rather paralleling the midrib. On P. balsamifera, the rows may follow the margin, midrib. parallel the midvein, or run at different angles on different parts of the leaf. Sometimes three or four rows of galls will occur on the broad part of the leaf. 

The stem mother usually has 5-jointed antennæ and is wingless. The winged individuals of the second generation emerge from the galls within a period of a few weeks. The mouth of the gall opens slowly, finally permitting the winged female to emerge. Predators frequently enter the opening galls and kill the pupal nymphs. Several species of syrphid larvæ and a small hemipterous insect were the forms most commonly observed in Utah. 

Wingless females were numerous in the galls at St. George, on July 9, 1925. 

This species has been collected in Utah from Blacksmith Fork Canyon, Cedar City, Eden, Farmington, Hyde Park, Murray, Logan, St. George, Salt Lake City, Santa Clara, and Smithfield.  

Thecabius populi-conduplifolius (Cowen). 

This aphid folds the leaves of balsam poplar, Populus balsamifera and P. deltoides, producing a pseudogall along the midvein or parallel to it. The stem mothers may be found in galls near the margin of the leaf. The young of the stem mother do not remain in the gall with her, but migrate to the new leaves at the tips of the branches. All of the second generation become winged. They migrate to Ranunculus sp. where the third and several subsequent generations of apterous viviparous females are produced. These summer colonies give a cottony appearance to the base of the Ranunculus leaves and stems. The fall migrants (sexupara) appear during late summer and fall and migrate back to the cottonwoods where the sexual forms are produced. 

Galls of the second generation are always on terminal leaves. However, late in the season, after the stem mother ceases producing, new terminal leaves are produced which do not become infested. 

At Fruita, and along the stream below Capital Bridge, nearly all of the leaves on the young poplars were folded on June 27, 1926. By this time most of the aphids had migrated. Many of the aphids had been parasitized, but a few living specimens were obtained. These aphids were quite numerous in the galls at Randlett on July 14, 1927, and less so at the same time in the few collections made at Fort Duchesne and Vernal. Ordinarily, quite a number of aphids occur in each gall. When they were examined at St. George on July 9, 1925, only a few specimens remained in galls. Winged females were becoming abundant at Plain City, by June 15, 1928. 

Pemphigus populi-caulis Fitch.

[Two drawings of the gall appear on page 9 of the pdf]

The Gall.—The gall is semi-globular. Large ones attain a diameter of 1/2 inch or more. Normally located galls are at the base of the leaf where the blade and petiole unite. The gall is composed of the thickened and twisted petiole and a very small portion of the base of the leaf blade which frequently extends a short distance down onto the gall. The greater part of the gall extends below the plane of the leaf blade. Viewed from above the mouth is normally not visible and the midrib and the first diagonal veins on either side are seen to merge into the body of the gall. 

When viewed from below the midrib is seen to bend abruptly and to merge with a ridge formed by the edge of the petiole which follows the curve of the gall and forms a part of one lip of the opening. The other lip of the opening is formed by a fold in the base of the leaf blade for a part of its length and the balance by the edge of the petiole. The petiole is twisted so that the flattened portion lies in nearly the same plane as the leaf blade instead of at right angles to it as in normal leaves. It is clear that almost the entire gall is made up of the much enlarged and twisted petiole. The mouth is usually full-lipped and extends more or less in a spiral fully 2/3 the distance around the gall. Many times there is a small round opening at some point along the lips through which the winged lice escape. The senior author has collected aphids which correspond in every respect to P. p. -caulis, from galls similar to those produced by P p.-venae at Oak Park MN, and in the Bitter Root Valley in MT. These were from Populus balsamifera trees heavily infested with P p-globuli and P. p-venae. It seems than under certain conditions at least P. p-caulis produces galls on the leaf similar to those produced by P. p.-venae. 

This aphid was very abundant in Logan during the spring of 1925. The infestation was so severe that by July 1st many leaves had fallen from the infested poplars, Populus balsamifera and P deltoides. About 3 percent of the leaves remaining on the trees were infested with galls.

The aphids are ordinarily very numerous in these galls, and sometimes a hundred or more pupal nymphs and winged females in addition to the stem-mother are present in a single cell. Ordinarily, there is a large drop of liquid in the bottom of the gall. The waxy material secreted by the wax glands makes the inside of the gall grayish so that when it is opened, the moving aphids appear to be mixed up in a growth of fungus.

In addition to being present in Logan, this aphid was also found in Big Cottonwood Canyon, Utah, on June 29, 1925, where it was producing its characteristic galls. it has also been collected at Hyde Park during early July, 1928.

Notes:

Pemphigus populi-caulis and Pemphigus populi-globuli were described by Dr. Asa Fitch in the " Report of the Noxious and Other Insects of the State of New York," 1859. 

Fitch's descriptions of the insects are too meager to make a separation of the species certain without the galls. 

The gall produced by the aphis Fitch described as P. p.-caulis is described as a "bullet-like gall " on the middle of a leaf stalk from a Lombardy poplar. This gall was found on the 27th of June, three years before the description of P. p.-caulis was publishéd. 

Discussing the gall further, Fitch says: "When the leaves fell from this tree in autumn, a few were found among them, more faded than the others and having these same excrescences, but placed at the base of the leaf instead of on the middle of its stem"

Farther on in his discussion, Fitch states: "Galls analagous to those here described grow upon the leaf stalks of the Lombardy and Black poplar in Europe, from attacks of the Pemphigus bursarius of Linnaeus. " 

After comparing it with specimens of that species and its galls, Fitch considered his aphid different from P. bursarius, the fly being paler in its color, and its gall because of spirally coiled somewhat like the shell of a snail."

It is very evident from Fitch's discussion that he had in mind, when he described P. p.-caulis, a gall located on the petiole of the leaf at some distance from the leafblade, and one produced by a twisting of the petiole into a spiral. 

It is quite probable that the petiole gall described by Fitch is not typical of P. p.-caulis, but that those at the the base of leaf which he mentions as being taken in the fall are the typically located galls. 

The aphid herein figured and described as Pemphigus populi-caulis is from galls located at the base of the leaf and produced by a twisting or spiralling of the petiole. The species described as P. p.-globuli, is considered to be the globuli of Fitch because of the likeness of its gall to the one described by Fitch in his discussion of that species. 

Since the original descriptions of P. P.-caulis and P. P.-globuli were published these species have received much attention, if we may judge from the frequent references to both. However, in spite of this, several aphidologists appear to have failed to distinguish between them. 

P. p.-caulis and P. p.-globuli are very similar structurally and their galls are, in a general way, much alike, although quite different when studied in detail. This general similarity of both the aphids and their galls appears to have caused considerable confusion in the literature. This was probably increased by a lack of detail in the earlier descriptions. 

In studying the two species under discussion, the senior author has collected material from several states and in many localities in some of these states. When collections of both species have been made in the same locality, they rarely have been found on the same host species. In Colorado and Utah P. p.-caulis was taken on Populus deltoides and P. p.-globuli on Populus angustifolia and Populus balsamifera. In California P. p.-caulis was taken on Populus Fremontii and P. p.-globuli on Populus trichocarpa. P. p. -caulis was taken on Populus deltoides at St. Cloud, Minnesota, and both species on Populus balsamifera at Oak Park, Minnesota. East of the Rocky Mountains in Montana P. p.-caulis was taken on Populus deltoides and P. p.-globuli on Populus angustifolia. P. p.-caulis was taken on Populus balsamifera in the Bitter Root Valley of Western Montana and P. p.-globuli on the same species of Populus near the Flat Head Lake. The junior author reports both species on Populus balsamifera. These observations appear to indicate that Populus balsamifera is the only common host of P. p.-caulis and P. p.-globuli east of the Rocky Mountains. Populus trichocarpa may serve as a host for both in the range of this tree. 

These collections have been carefully separated according to the type of gall and a large series of the aphids from each gall type critically studied. These studies have brought to light certain structural differences by which P. p.-caulis and P. p.-globuli alate forms from the galls may be separated. These differences are constant in relative magnitude but not in actual magnitude. 

Both species under discussion are quite variable in size and in some other characters. This necessitates studying several individuals and comparing the means of characters in order successfully to separate them. When a sufficient number of individuals to make a representative population is studied, separation becomes easy and certain. 

Thomas, in the "Third Annual Report on Noxious and Beneficial Insects of Illinois," 1879, pictures a typical Pemp. populi-globuli gall for the gall of Pem. populi-caulis. Dr. O. W. Oestlund described Pem. populi-caulis in his synopsis of the Aphididæ of Minnesota. His description is not sufficiently detailed to determine which of the two species under discussion he really had. The host is given as Populus monilifera. 

Essig, in Pomona College Journal of Entomology, 1912 describes and illustrates Pem. populi-caulis and several galls. These galls are of 3 quite distinct types. One is typical galls. of Pem. p.-caulis. Several are typical Pem. p.-globuli and one is typical of what the senior author is calling Pem. p-venae. The senior author has collected all three types of galls on Populus trichocarpa in California. The aphids from the typical Pem. p.-globuli and Pem. p.-caulis were the ones used in the studies already referred to. The ones from the other type of gall do not fit with either Pem. p.-caulis or Pem. p.-globuli. Several collections of these galls have been made in Minnesota. The aphids from Minnesota differ from the species being discussed in the same way as those from California. This species is described later as Penz. P.-venae. The descriptions of Essig are not sufficiently detailed to enable one to determine his species with certainty. However, his figures of the antenna, of the alate viviporous female and the stem mother are typical of Pem. p.-caulis.

It seems quite probable that Essig failed to separate the 3 species in his material. 

Dr. Edith M. Patch described Pem. populi-caulis from Populus balsamifera and pictures 1 typical Pem. populi-globuli gall and 2 not typical of this species or of Pem. populi-caulis. The latter are similar to galls taken by the senior author at Oak Park, Minnesota, produced by what he calls Pem. populi- venæ.

Pemphigus populi-globuli Fitch

The Galls.—The galls are usually semi-globular. Not infrequently they are more or less cone-shaped. Normally located galls are situated at the base of the leaf, on its upper side. The color is green, or when exposed to the tinged with reddish varied with yellow. The gall is composed of a much enlarged and thickened portion of the leaf blade. On the under side there is a somewhat curved mouth-like orifice bounded on one side by the much thickened midrib and on the other by a thickened fold in the leaf blade. A more or less broken portion of the blade usually extends along this fold nearly the entire length of the mouth. 

Many times the blade of the leaf stands at an angle to the petiole. The opening in the gall is rarely equal to one-half the circumference of the gall and is not visible from above. The lip-like borders of the opening are frequently quite rough. Galls located at some distance from the base of the leaf and resembling those produced by P. P.-venæ sometimes occur, especially on heavily infested trees. 

This aphid is frequently encountered in Utah, on balsam poplar, Populus balsamifera. It has been collected in this state from Big Cottonwood Canyon, Blacksmith Fork Canyon, Farmington, Hyde Park, Providence, and Salt Lake City. The material described was collected at Salt Lake City. 

Pemphigus populi-transversus Riley

This aphid has, as its summer host, plants belonging to the family Cruciferæ. Jones states that Populus balsamifera, P. monilifera, P. trichocarpa and P. fremontii have been mentioned as hosts. He also gives cabbage, turnip, mustard (Brassica nigra), cauliflower, broccoli, (B. oleracca botrytis), Brussels sprouts, rape, and several weeds belonging to the family cruciferæ as hosts of the subterranean forms. While this aphid has been reported as damaging certain cruciferous crops in the south, no damage in the northern portions of its range has been reported. In Utah this aphid was collected at Farmington, on June 28, 1923. At this time spring migrants and pupal nymphs were present in galls formed on the petiole near the leaf of cottonwood, Populus deltoides. Galls and stem-mothers apparently of this species, were collected at Santa Clara by Dr. H. J. Pack, during June, 1928. 

Pemphigus populi-venæ Fitch

Pemphigus Populi-venæ was described by Dr. Asa Fitch in 1859. Since the original description was published, this species does not appear to have been recognized but appears to have been confused by some aphidologists with P. p.-caulis and P. p.-globuli. 

In his studies of this species Dr. Fitch appears to have failed to recognize the real nature of the aphids in the galls. It seems altogether probable that his male and female larvæ and pupæ were the early stages of the alate females (fundatrigenia).

The winged individuals were so briefly described by Fitch that the description is valueless for purposes of identification. Identifying aphids by the plant deformities produced is very apt to lead to confusion. Easily distinguished species produce very similar deformities and a single species may produce more than one form of deformity. 

The Galls.—Dr. Fitch describes the galls of P. P.-venæ as "an oblong compressed excrescence like a cock's comb, of a light red color varied with pale yellow growing from the midrib of balsam poplar leaves on their upper side with an orifice on the opposite side. They are nearly semi- circular and half as high as long, being usually over a half inch in length, with uneven surface, their walls thick, brittle and succulent. They are commonly placed near the base of the leaf but sometimes in its middle." 

Galls similar to those described by Fitch were collected by the senior author at Oak Park, Minnesota, on balsam poplar and near Spreckles, California, on Populus trichocarpa. 

The aphids from these galls have some of the characters of P. p.-caulis and P. P.-globuli but are not wholly like either. The most noticeable difference between P. P.-venæ and P. p.-caulis and P. P.-globuli is its smaller size. The senior author has taken all three species on a single balsam poplar tree in Minnesota. Because of the similarity of the size of these species to those described by Dr. Fitch and the likeness of the galls of P. p.-venæ as described by Dr. Fitch to those collected in Minnesota and California, the aphid here described is considered the P. p.-venæ of Fitch. 

The Gall.—Dr. Fitch's description of the gall should be enlarged by stating that the galls vary in form from more or less oblong to semicircular and even almost triangular in outline. On heavily infested trees galls occur on both sides of the leaf. When on the underside they may be confused with those of P. beta, being similar in form and location. 

Aphids collected at Hyrum, Utah, on June 20, 1926, seem to be the species described by Fitch. These aphids were producing galls on the leaves of the narrow-leaved cottonwood, Populus angustifolia. 

Pemphigus populi-ramulorum Riley.

[Drawings of this gall appear on page 17 of the pdf]

While this species was described from material collected on Populus balsamifera it occurs commonly on Populus deltoides in localities outside the range of the balsam poplar. This species resembles quite closely both P. p.-caulis and P. p.- globuli. 

This aphid is frequently encountered in Utah and is particularly interesting because of the gall it produces on the young twig bark of poplars, especially Populus balsamifera. Collections made at Leeds, both from twig galls and from galls below the bases of the leaves on the petiole, indicate that this one species produces two types of galls. This is a rather uncommon occurrence among gall-forming aphids. The openings to the leaf galls are often slightly beaked, and the mouth does not always open along the same axis, which gives variation in appearance to the openings of different galls. 

In Utah this species has been collected from Benjamin, Benson, Farmington, Holliday, Hooper, Leeds, Provo, St. George, Santa Clara, and Zion National Park. 

Pemphigus betæ Doane.

A pemphigid from beet roots grown at Pullman, Washington, was named "Pemphigus betae" and described by Doane in 1900. In 1910 Williams described Pemphigus balsamiferae. This aphid was taken at Squaw Creek, Nebraska, on Populus balsamifera. In 1914 the senior author discovered that the sugar-beet root-louse in Colorado is the summer and fall generations of P. balsamiferae from the narrow-leaved cottonwood, Populus angustifolia. Unless the beet is the host of two Pemphigus species and the one in Washington is different from the one feeding on beets in Colorado, P. balsamiferæ Williams, becomes a synonym of P. beta Doane. In this discussion P. balsamiferæ is considered the spring form of P. betae. 

P. betae occurs on the balsam poplar within the western range of this tree and on Populus angustifolia where this tree occurs naturally. Its galls are located on the underside of the leaf. They may easily be confused with the galls of P. p.-venæ. 

The following unpublished chapter in the life history of P. betae was worked out by the senior author in 1921. 

Hibernating aphids were collected from the soil November 2d. These were confined in salve boxes in a greenhouse under ordinary greenhouse temperatures. The aphids collected November 2d. are designated the first generation. The second generation (young of the hibernating lice) appeared December 31st after nearly 2 months' inactivity on the part of the hibernating individuals. The third generation appeared January 21st; the fourth generation, February 24th ; the 5th, March 12th ; the 6th, March 24th; the 7th, April 8th, and the 8th, April 29th. 

The age of the various generations when reproduction began was: second generation, 21 days old; third, 34 days; fourth, 16 days; fifth, 12 days; sixth, 15 days; and seventh, 21 days. The variation in ages is probably due to variations in temperature and the condition of the food supply. Low temperatures retard development and high temperatures quicken it. 

The first, second, third, fourth, and fifth generations were all apterous viviparous females which began reproducing immediately upon becoming mature. The first alate forms (sexuparæ) appeared in the sixth generation. The sixth and seventh generations were composed of about equal numbers of apterous viviparous females and alate sexuparæ. The apterous females of the sixth and seventh generation began to reproduce as soon as mature. The offspring of the sixth generation were of four kinds. Those of the apterous forms were apterous viviparous females and sexuparæ; those of the sexuparæ, true males and females. The offspring of the seventh generation (the eighth generation) were of four kinds also. Those of the apterous viviparous females were apterous forms and sexuparæ. The fortner ceased feeding and became inactive upon reaching mature size. They sought out crevices in the soil where they became completely covered with the wax secreted by their wax glands. Those of the sexuparæ were true males and females. The hibernating forms of the eighth generation differ from the apterous forms of the sixth and seventh generations, since upon reaching sexual maturity they produce only apterous forms. 

This change into hibernating forms appears to be biological function and not a temperature reaction. 

This aphid has been collected in Utah from the following localities: Amalga, Benson, Brigham, Collinston, Cornish, Delta, Garland, Hoytsville, Hyde Park, Lehi, Lewiston, Logan, Madison, Millville, Richfield, Richmond, Salt Lake City, Smithfield, and Trenton. 

Prociphilus fraxinifolii (Riley).

Prociphilus fraxinifolii differs from typical Prociphilus species in the nature of the individuals composing the various generations. The following observation was made by the senior author at Longmont, Colorado, in 1925.

A young white ash tree in one of the city parks was very heavily infested with Proc. fraxinifolii on June 18. At this time many first instar lice were travelling from the infested tips of the branches toward the trunk of the tree. Upon reaching the trunk, these young lice travelled up or down until another branch was reached, when they started toward its tip. It was thought that the migrating lice might be in search of fresh leaves upon which to locate. 

At the time of observation some curled leaves contained stem mothers and many large mature apterous females which were giving birth to the young already mentioned. Others contained only a limited number of these young. 

A cluster of curled leaves containing the stem mothers and apterous females was removed and fastened to a branch of a young ash tree that had no curled leaves. Immediately . the young were observed travelling toward the trunk of the tree. The second day after the curled leaves were placed on the young tree, the leaves of nearly every branch below the point where the curled leaves were attached were badly curled. 

On the fourth day no leaves above the point where the curled leaves were attached to the branch were curled. The migration of young, therefore, appears to be mainly downward. The third and fourth day after the curled leaves were placed on the young tree they were completely dry and the mature lice in them were dead. Apparently the stem mothers and second generation apterous females do not migrate. 

This observation indicates that the sequence of generations of Proc. fraxinifolii is somewhat similar to that of Eriosoma species. No winged individuals were secured. It is believed that the winged lice are produced by the migrating generation (the young of the second generation), and, therefore, belong to the fourth generation. 

The tribe Pemphigini (Aphididae) in Utah