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PSYCHE
A JOURNAL OF ENTOMOLOGY
EsTABLISHED IN 1874
VOL. XXV FEBRUARY, 1918 NUMBER 1
Prodryas persephone Scudder.
CONTENTS.
The Genus Narnia Stal, and a Key to the Genera of Anisoscelini A. and S. (Coreidz: Heteroptera). Edmund H. Gibson and Abby Holdridge
A Phylogenetic Study of the Terga and Wing Bases in sees, spake Dermaptera, and Coleoptera. G.C.Crampton ..
On the Occurrence of a Mermis Epidemic Amongst rece hou per R. W. Glaser and A. M. Wilcox : ; d
The Pulsatile Vessels in the Legs of Aphidide. Chas. H. Richardson Ascogaster Carpocapse, a Parasite of the Oriental Moth. A. M. Wilcox
Exchange Column
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gon Oly te
A Journal of Entomology
Volume XXV
1918
EDITED BY CHARLES T. BRUES
Published by the Cambridge Entomological Club, Bussey Institution, Forest Hills, Boston, Mass., U.S. A.
Eee els!
VOL. XXV FEBRUARY, 1918 No. |
THE GENUS NARNIA STAL, AND A KEY TO THE GENERA OF ANISOSCELINI A. AND S. (COREIDE: HETEROPTERA).
By Epmunp H. Grsson and Appy Ho.uprince, Bureau of Entomology, Washington, D. C.
Members of the genus Narnia Stal present an interesting group in the tribe Anisoscelini A. and S. as well as presenting difficulties to the systematist. In 1862 Stal described the genus to include his femorata and later, in 1870, he described N. pallidicornis, both descriptions being made from single specimens. Since then three other well defined species have been added to the genus. Now, from the study of a large series of specimens it appears that Stal’s two species are the same and one species, with the name femorata retained. The cltaracters which he gives for separating /pallidi- cornis from femorata can not be termed stable, such as the color of the basal joint of the antenne, which varies to a considerable de- gree in nearly every species of the tribe. The late Mr. Otto Heidemann was of the same opinion as the present authors in this matter. Mr. E. P. Van Duzee, Entomological News, Vol. XVII, No. 10, pp. 384, 1906, has also voiced a similar belief when he stated that he suspected femorata to be a northern form of pallid- icornts. |
Mr. Van Duzee considers his species snowi and wilsont as form- ing a subgenus to which he gives the name Xerocoris. In this respect the authors disagree with Mr. Van Duzee and state that if there is to be any dividing of the genus it should be so as to group femorata and snow? together and inornata and wilson together. Such a grouping would be based upon the form of the dilation of the hind tibiz which is quite generally accepted to be of greater importance than the relative breadth of insect and con- nexium, and form of prothorax. It seems quite unnecessary to recognize subgenera in Narnia.
2 Psyche " [February
Narnia Stal.
Narnia Stal, Stett. Ent. Zeit., Vol. 23, p. 294 (1862).
Head elongate, horizontal. Antenne rather stout but not swollen or dilated, basal joint short, shorter than length of head; rostrum passing the metasternum, buccule short. Thorax longer than head, broad and rounding posteriorly. Elytra nar- rowing towards apex. Hind femora more or less swollen, hind tibize with small dilations or foliations. Narnia may be separated from Leptoglossus by the smaller dilation of the hind tibiz and shorter basal joint of antenne.
Key to the Species.
1. Dilation of hind tibia reaches two-thirds the length of tibia... .2- Dilation of hind tibia reaches three-fourths the length of tibia. .3 2. Elytra with distinct, broad, white band; width comparatively
STORE 0. ir cedhcte da tae es 5 snowt Van D. Elytra without distinct white band, sometimes a slight trace of one; width comparatively narrow............femorata Stal
3. Species small, apex of head, basal joint of antennz, and legs TOC: , sacerete! Apteutee ae ers ena, eee Soe wilsont Van D. Species larger, no distinct red colorations. ..... inornata Dist.
Narnia femorata Stal.
Narnia femorata Stal, Stett. Ent. Zeit., Vol. 23, p. 296 (1862). Narnia pallidicornis Stal, Enum., I, p. 166 (1870).
This species can be distinguished from all others by the short stout dilation on the hind tibiz and without band across elytra.
The species occurs in California, Arizona, Texas, Mexico and Guatemala.
Narnia snowi Van D.
Narnia snowt Van Duzee, Ent. News, Vol. XVII, No. 10, p. 384
(1906).
The distinct broad white band across the elytra and broader form will readily distinguish this species from femorata Stal.
It is recorded from California, Arizona and New Mexico.
Narnia inornata Dist.
Narnia inornata Distant, Biol. Cent. Amer., Vol. I (1880-93).
This species may be readily distinguished by the long slender dilations of the hind tibiz, and lack of reddish colorations.
This western species occurs in Arizona, California and Mexico.
1918] Gibson and Holdridge—The Genus Narnia Stal 3
Narnia wilsoni Van D.
Narnia wilsoni Van Duzee, Ent. News, Vol. XVII, No. 10, p.
384 (1906).
Wilsoni differs from all other species in that it is much smaller, and has red colorations on apex of head, basal joint of antenne, and legs.
This species occurs in California.
A Key to the Genera of Anisoscelini A. and S.
The following key includes all of the genera of the tribe Ani- soscelini A. and $. Representatives of but three of the genera, Chrondrocera Lap., Leptoglossus Guer. and Narnia Stal occur in American north of Mexico, the other genera being limited to Cen- tral and South America.
The tribe may be characterized as follows: Head elongate, antenne long and more or less slender. Thorax trapezoidal in form, greatly depressed anteriorly, posterior lateral angles more or less acutely angled. Posterior femora sometimes swollen but not incrassated. Posterior tibiz with a broad thin dilation or fo- liation which is often wider than the width across the elytra.
The genera may be considered as grouped into two divisions, Anisoscelaria n. n. those having the joints of the antennz simple as in Anisoscelis and Chrondroceraria n. n. those having the joints of the antennz more or less dilated as in Chrondrocera.
The authors feel justified in placing Stenoscelidea within this tribe as the characters of the hind tibiz are of greater importance than the form of the antenne.
1. First joint of the antennz much longer than the second Uranocoris Walk. First segment of the antenne not longer than the second, often
CHECHELS SIN CETg Re) 2 9 2 67 Sia RU et ea an ee RE Q 2. Segments of antennz prominently dilated................. 8 Bepments Or antemnee Not dilated... 0)... 8 ow ee 3
3. Basal joint of antenne short, shorter than length of head Narnia Stal Basal joint of antennz long, as long or longer than length of
LOTT OCS Ea as, ey Ger ie te See Se nA Ca eee nen 4 4. Basal joint of antennz equal to length of head, or slightly | UN i OU eet aa ee ee Oe ae Leptoglossus Guér.
Basal joint of antennz very much longer than length of head, 5
‘4 Psyche [February
5. First and fourth segments of antenne incrassated Microphyilia Stal First and fourth segments of antennze not incrassated....... 6 6. Width of dilation of posterior tibiz less than width across GLVET Se ASG eh ote Se oe Beene Stenoscelidea Hope.
élytra cick, hae by ee Gee oe ee 7 7. Length of basal joint of antenne less than twice the length of head | 327.0; eb) a ee eee Diactor Perty. Length of basal joint of antennz at least twice the length of head. :.e0s4 wins Oe ee See ee Anisoscelis Latr. 8. Second segment of antenne dilated, third also dilated....... 9 Second segment of antenne simple, third dilated, Baldus Stal
9. Second segment of antennz dilated on both sides Chrondrocera Lap. Second segment of antenne slightly dilated above, not below, 10 10. Posterior lateral angles of thorax produced, or sharply angled Holymenia Stal Posterior lateral angles of thorax not at all produced........ Tarpeius Stal
A PHYLOGENETIC STUDY OF THE TERGA AND WING BASES IN EMBIIDS, PLECOPTERA, DERMAPTERA, AND COLEOPTERA.!
By G. C. Crampton, Pu.D., Massachusetts Agricultural College, Amherst, Mass.
In a previous paper, the Plecoptera, Embiids, Hemimerids, and Dermaptera, were grouped in a superorder called the Panplecop- tera, and a further study would indicate that the Coleoptera might be included in this group also. There is some doubt as to the Strepsiptera, but certain features point to a rather close relation- ship between them and the Coleoptera (as is generally thought to be the case, although the investigations of Pierce, 1909, have thrown some doubt upon the current idea of their affinities) and it is quite possible that the Strepsiptera should likewise be included in the superorder mentioned above.
1 Contribution from the Entomological Laboratory of the Massachusetts Agricultural College, Amherst, Mass.
1918] Crampton—Study of Terga and Wing Bases 5
The Plecoptera, with the Embiids, are very like the ancestors of the insects comprising this superorder, (the Panplecoptera) while the Dermaptera form an offshoot which approaches the Isoptera in many respects—but the strongest affinities of the Isoptera seem to be on the side of the forms comprising the superorder Pandic- tyoptera (composed of the Isoptera Zoraptera, Blattids and Man- tids). The Coleoptera have branched off very near the Dermap- tera, and have retained certain ancestral features occurring in the Embiids and Plecoptera, but their line of development has appar- ently paralleled that of the Dermaptera quite closely. Some representatives of the Coleoptera exhibit certain features sugges- tive of those found in the Blattids; and other Coleoptera have retained certain structures (particularly in the larval stages) sug- gestive of Neuropteron affinities. However, since both the Pan- plecoptera and the Pandictyoptera are descended from common ancestors (which were not unlike the fossil Palaeodictyoptera) it is not surprising that certain features inherited from their common ancestors, should be carried over into both groups; and similarly, since both the Panplecoptera and the insects grouped about the Neuroptera were descended from similar ancestors (the ancestors of the Neuroptera were probably very similar to the Plecoptera) it is not surprising that similar characters should reappear in both the Neuroptera and Coleoptera. At any rate, the closest affinities of the Coleoptera seem to be with the Dermaptera, rather than with the Neuroptera (or with the Blattids) so far as the adult characters are concerned. : |
The Embiids are extremely closely related to the Plecoptera, as is shown by the character of their thoracic sclerites, legs, etc.; and the fact that the cerci of the Embiids are reduced, does not militate against the argument for the close relationship between the two orders, since certain Plecoptera also have the cerci reduced to two segments.
In both Embiids and Plecoptera, the body is more elongate, and the tergal region of the wing-bearing thoracic segments shows a marked tendency toward becoming longer than broad, in contra- distinction to the condition found in the Coleoptera and Dermap- tera, in which the tergal region exhibits a tendency to become broader than long, as may be seen by comparing Figs. 1 and 3 with Figs. 2 and 4. Inthe Embiids and Plecoptera, there is a prescutal
6 , Psyche [February
region “‘psc’’ demarked in both segments (Figs. 1 and 3), and situated well in advance of the wing bases, while the prescutal region is not so clearly demarked in the Coleoptera and Dermap- tera (Figs. 2 and 4), and, when present in the latter insects, it is situated on a line with, or back of, the wing bases (or rather the anterior margin of the wing bases).
In the Plecoptera and Embiids, there is a well developed mes- othoracic postscutellum (“psl,’’), while the mesothoracice postscu- tellum is not developed in the Coleoptera and Dermaptera, nor does the metathoracic postscutellum (“‘psl3;’’) dip downward at such a marked angle in the Coleoptera and Dermaptera (Figs. 2 and 4) as in the Embiids and Plecoptera (Figs. 1 and 3). The tegula (“tg’’) is well developed in both segments in the Embuds and Plecoptera (Figs. 1 and 3) while it seems to be lacking in the Cole- optera and in the metathorax of the Dermaptera, although the mesothoracic sclerite labeled ‘“‘tg’”’ in Fig. 4 is interpreted as the tegula in the Dermaptera, by Pantel, 1917, in his excellent mono- graph of the thoracic region of these insects.
In the Coleoptera (Fig. 2) a myodiscus, or muscle disk “d,”’ to which are attached certain muscles connected with flight, occurs in the metathorax, and might be mistaken for the tegula. It is homologous with a smaller disk labeled “d”’ in the metathorax of the Dermaptera (Fig. 4, “d’’) which corresponds to the small disk “qd” near the tegula “tg’’ of the mesothorax of the same insect (Fig. 4); and a similar small disk “‘d”’ occurs near the tegula in both mesothorax and metathorax of Plecoptera (Fig. 1). Snodgrass, 1908, in his earlier work, which was incorporated in his more exten- sive studies of the thoracic sclerites and wing bases of insects (Snodgrass, 1909) refers to the sclerite in question as the “muscle disc”? in Coleoptera, but does not seem to have found it in other insects. Pantel, 1917, interprets the sclerite “d’’ in the meta- thorax of the Dermaptera (Fig. 4) as an intersegmental plate.
The terms axillaries, alar ossicles, and pteralia, have been applied to the little plates by means of which the wings articulate with the tergal region, and in a paper dealing with the nature and origin of the wings of insects (Crampton, 1916) it was pointed out that the alar ossicle “np” (termed the notopterale) is probably a detached portion of the notum or tergal region of the segment. A further examination of these alar ossicles would tend to confirm this sup-
1918] Crampton—Study of Terga and Wing Bases ff
position, since in the Embiids (Fig. 3), the alar ossicle “np” evi- dently is a portion of the notum which is not yet completely de- tached, while in the Plecoptera (Fig. 1, ““np’’) it likewise extends for some distance closely applied to the lateral margin of the notum. The only winged Embiid which I have for examination is the male of Embia major shown in Fig. 3, but it is very probable that other Embiids will exhibit a type of alar ossicle similar to the elongate ““notopterale” ““np”’ of the Plecoptera (Fig. 1), and even in the Embiid shown in Fig. 3, the alar ossicle “np” is much longer than the homologous sclerites “np” of Figs. 2 and 4.
In the metathorax of both Dermaptera and Coleoptera (Figs. 2 and 4) the sclerite “np”’ is very similar in outline, and in position, being situated much further forward than in the Embiids and Plecoptera (Figs. 1 and 3), and it is not so elongate as in the Em- biids and Plecoptera, as was mentioned above. In the mesothorax of the Dermaptera (Fig. 4), this plate “np2’’ has become broken up into two parts, the anterior one of which is bent abruptly down- ward. This has resulted in the incorrect homologizing of the parts of this plate in the mesothorax of the Dermaptera, by some investi- gators, but the two parts of the mesothoracic plate “np,”’ of Fig. 4 are clearly homologous with the single metathoracic plate “np3”’ of the same insect.
Snodgrass, 1908-1909, refers to the mesothoracic plate “tg (Fig. 4) of the Dermaptera, as “‘a small rod in wing base,” appar- ently not realizing its true nature; but Pantel, 1917, correctly refers to it as the tegula. While the tegula “tg” is well developed in both meso- and metathorax in the Embiids and Plecoptera (Figs. 1 and 3), I do not think that it is developed in the metathorax of the Coleoptera and Dermaptera, unless the region designated as “+t” in the metathorax of the Dermapteron shown in Fig. 4 repre- sents the tegula. Pantel, 1917, refers to the region “‘ptg”’ in the metathorax of the Dermapteron shown in Fig. 4, as the metatho- racic tegula, but this region seems to correspond to the so called parategula of Hymenoptera and Diptera (shown in Fig. 4 “‘ptg”’ of the wing base of a Dipteron, by Crampton, 1914,).
Pantel, 1917, considers the metathoracic sclerite “‘sus” of the Dermaptera (Fig. 4) as one of the pteralia, or articulatory ossicles at the base of the wing. As far as I can judge, however, the region “su” of Figs. 1, 2, 3, and 4, is merely an antero-lateral marginal
>
8 Psyche [February
region of the tergum called the suralare (Crampton, 1914-1916) and serves as one of the pivots for the wing in the movements of flight, although it may become detached from the remainder of the tergum in a few rare instances, as Pantel considers to be the case in the Dermaptera. ‘The posterior wing process “‘a”’ of the meso- thorax is very similar in both Coleoptera and Dermaptera (Figs. 2 and 4), being rather long and slender in these insects, while it is shorter and more blunt when it occurs in other members of the group (Fig. 1, ‘‘a”). The basanal pterale “sa” is proportionately much larger in the metathorax of the Coleoptera and Dermaptera (Figs. 2 and 4) than in the Plecoptera and Embiids (Figs. 1 and 8).
In both the Coleoptera and Dermaptera (Figs. 2 and 4) there is a pronounced tendency for the tergal region of the wing bearing segments to become broader than long, and, with the Strepsiptera, and certain Orthoptera, these insects comprise the few forms in which the metathorax surpasses the mesothorax in size. Unlike the Plecoptera and Embiids, there is a well marked tendency in the Coleoptera and Dermaptera (Figs. 2 and 4) for the mesonotum to take on a triangular outline, and for the scutellar region of the mesonotum to become pointed posteriorly and to overlap the an- terior portion of the metanotum behind it. Correlated with this tendency for the scutellum of the mesonotum to overlap the meta- notum in the Coleoptera and Dermaptera, there is a well marked tendency toward the reduction of the mesothoracic postscutellum, which is well developed in the Embiids and Plecoptera.
In the metathorax of Coleoptera and Dermaptera (Figs. 2 and 4) two alar ridges or ‘“‘alacristae”’ labeled “‘ac”’ serve to hold the elytra in place when at rest, and in many Dermaptera, they are provided with bristles which doubtless aid in holding the elytra in position. In both Coleoptera and Dermaptera, the metathoracic scutum is traversed by a “‘transscutal suture” (“‘tr”’ of Figs. 2 and 4) which is apparently absent in most of the other members of this superorder; and it is at once apparent from the study of the tergal region and the wing bases, that the Coleoptera are very similar to the Dermaptera in regard to these features, while the Embiids are very similar to the Plecoptera in the character of their tergal regions and wing bases.
The presence of the posttergal fold “pt” of Fig. 4 is a “ Pandic- tyopterous”’ character (well developed in Isoptera, Mantids, etc.)
1918] Crampton—Study of Terga and Wing Bases 9
which has been retained in the Dermaptera, but has become lost, or was never developed, in the Coleoptera. A suggestion of this fold is also retained in the Plecoptera, as is shown in the posterior tergal fold designated as “pt” in the metathoracic region of the Plecopteron depicted in Fig. 1. There is a tendency for this region to become reduced, or to unite with the surface which it overlaps, so that the narrow continuation of the surface of this fold toward the point designated as “x” in the metathorax of Fig. 4, may possibly be homologous with the similar narrow continuation of the region beside the postscutellum, toward the point labeled “x” in Fig. 2 (at the base of the sclerite “sa’’).
In the foregoing descriptions, I have laid especial emphasis upon the resemblance between the Coleoptera and Dermaptera, as illus- trated by the preponderance in size of the metathorax over the mesothorax; the relative width, and the outlines of the nota; the triangular shape of the mesonotum, and its overlapping the meta- notum, with the consequent reduction of the mesothoracic post- scutellum; the development of ridges in the metanotum for holding the elytra in place; the formation of a transscutal suture; the retention of the myodisc rather than of the tegula in the metanotal region; the outline and extent of the pteralia, etc. Similarly, the marked resemblance between the Embiids and Plecoptera is shown in the relative size of the nota, the width and the outlines of the nota; the location of the prescutum in front of the anterior margin of the wing-base; the development of the mesothoracic postscutel- lum; the development of the tegulae in both segments; the elon- gate notopterale, ete. On the other hand, in emphasizing these similarities between the Coleoptera and Dermaptera. or between the Embiids and Plecoptera, one should not lose sight of the fact that the Coleoptera and Dermaptera are both related to the Em- biids and Plecoptera, although the Dermaptera, being the more primitive of the two, are nearer to the Embiids and Plecoptera than the Coleoptera are.
The cerci of certain larval Coleoptera, such as Galerita janus, and of certain Dermaptera such as Diplatys severa (in which segmented cerci precede the forceps of the adult forms) are very similar, even when the individual segments are compared together, and the cerci of both groups resemble those of the Plecoptera extremely closely, so that the evidence of the cerci would point to
10 | Psyche [February
a ‘‘Plecopteroid” ancestry for the Coleoptera and Dermaptera. The segments of the leg are very similar in Embiids, Plecoptera and Dermaptera, and the relationship of the Dermaptera to the Plecoptera is likewise shown by a comparison of the thoracic sclerites (or of the head region) of a nymph of the Plecopteron Perla with those of the Dermapteron Arixenia, the resemblance being very striking, as has been shown in a paper dealing with the thoracic sclerites of immature Pterygotan insects, which will soon be published. The tendency toward the shortening and thickening of the fore wings is quite marked in certain Plecoptera, and the pleural thoracic sclerites of the Embiids are in many respects very like those of the Dermaptera. In this connection, I would call attention to the fact that in the Embiids (Fig. 3) the nature of the postscutellar region of the metathorax and the first abdominal segment, with the bulging lateral regions, is very suggestive of the condition found in the Strepsiptera; but, since Dr. Pierce is mak- ing a comparison of the thoracic region of the Strepsiptera with other insects, which he finds more similar to the Strepsiptera than the Embiids are, the affinities of the Strepsiptera can be more accurately determined when the results of his extended studies are published.
Although the study of the terga and wing bases points to a close relationship between the Dermaptera and Coleoptera, and between the Embiids and Plecoptera, the evidence afforded by these struc- tures alone is insufficient to establish the affinities of the insects in question. On this account, a comparative study of the structures least subject to modification, and those situated in widely sepa- rated parts of the body, has been undertaken in order to demon- strate the relationships here proposed. Such an extensive treat- ment of the subject, however, requires more space and plates than can be afforded a single article; so that the summing up of the arguments for the relationships here proposed, can be more con- vincingly set forth after the evidence from the more extensive study of the parts has been presented in the proposed series of articles dealing with this subject.
BIBLIOGRAPHY.
1914,. Crampton—Notes on the Thoracic Sclerites of Winged Insects. Ent. News, 25, p. 15—(Sclerites of Dermaptera and Plecoptera figured).
1918] Crampton—Study of Terga and Wing Bases 11
1914, Crampton—On the Misuse of Terms, etc. Jour. N. Y. Ent. Soc. 22, p. 248—(Parategula shown in Fig. 4).
1916. Crampton—Phylogenetic Origin of the Wings, etc. Tbid., 24, p. 1—(Tergum and wing base of Plecopteron figured).
1917. Pantel—A proposito de un Anisolabis alado. Mem. Real Acad. Ciencias y Artes, 14, p. 3—(Numerous figures of terga and wing bases of Dermaptera).
1908. Snodgrass—A Comparative Study of the Thorax in Orth- optera, Euplexoptera, and Coleoptera. Proc. Ent. Soc. Wash., 9, p. 95—(Terga and wing bases of Dermaptera and Coleoptera figured).
1909. Snodgrass—The Thorax of Insects and the Articulation of the Wings. Proc. U. 8. Nat. Museum, 36, p. 511—(Terga and wing bases of Plecoptera, Dermaptera, and Coleoptera figured).
ABBREVIATIONS.
(The subscripts 2 and 3 denote mesothoracic and metathoracic structures respectively.) a...Adanal process (adanale) sometimes a detached plate, but usually serving as a pivot for wing in movements of flight. abd. First abdominal tergum. ac ..Alacrista, or alar ridges for holding elytra in place when at rest. d...Myodiscus, or muscle disc. m ..An alar ossicle, the medipterale. np. .An alar ossicle, the notopterale. p...Chitinous area possibly homologous with the parategula. pa. .Prealare, or prealar sclerite. pse . Prescutum. psl. . Postscutellum. pt .. Postplica, or posterior fold of tergal region. ptg . Parategula? s...Spiracle. sa ..An alar ossicle, the basanale. ss . .Scutal suture. su ..Suralar process (suralare) serving as a pivot for movements of
flight. t .. .Region homologous with tegula? tg . . Tegula.
tr . .Transcutal suture.
12 Psyche [February
EXPLANATION OF Puate I.
In all figures only a portion of the terga (which are symmetrical) has been shown, since the missing portions are exactly like those figured.
Fig. 1. Terga and wing bases of a Plecopteron.
Fig. 2. Terga and wing bases of the Coleopteron Photuris.
Fig. 3. Terga and wing bases of Embia major.
Fig. 4. Terga and wing bases of the Dermapteron Echinosoma.
ON THE OCCURRENCE OF A MERMIS EPIDEMIC AMONGST GRASSHOPPERS.!
By R. W. Guaser and A. M. Witcox.
While engaged in some investigations on grasshoppers, near Dummerston Station, southern Vermont, this past summer (1917), our attention was attracted to a high mortality amongst these insects (Melanoplus atlanis and M. bivittatus). The two species, especially M. atlanis, are extremely bad pests in this region of the country, attacking corn, wheat, oats and clover to such an extent that during certain summers the farmers become nearly frantic. Therefore, the high mortality amongst the grasshoppers, which appeared during the latter part of August and the early part of September, was exceedingly gratifying.
We soon discovered that this mortality was due to a species of Nematode belonging, as we supposed at the time, probably to the family Mermithidee. Subsequently (Sept. 20, 25 and Oct. 6), we sent large shipments of these worms to Dr. N. A. Cobb, of Wash- ington, D. C., for identification. Dr. Cobb was able to give us only a provisional identification on account of the utter absence of males in all of our shipments. We made collections of parasitized grasshoppers from a large variety of fields and as stated, sent a large number of specimens, but curiously enough no males were found. Dr. Cobb in a letter said: “Nothing I have learned would preclude your specimens from belonging to the same species as that referred to by Leidy under the name of Mermis ferruginea, which
1 Contribution from the Entomological Laboratory of the Bussey Institution in codperation with the U. S. Bureau of Entomology. Bussey Institution, No. 146.
Psycup, 1918. Vou. XXV, Puate I.
Crampron—Terga and Wing Bases.
1918] Glaser and Wilecox—A Mermis Epidemic amongst Grasshoppers 13
he says was common in Locusta carolina near Philadelphia; but there can be no certainty about the matter until males of the pres- ent species are obtained and a comparison made with Leidy’s material, which may or may not be in existence.” Dr. Cobb further stated that after the nematodes leave the grasshoppers, they make their way into the soil and that their further history is obscure.
In Vermont the nematodes parasitized both M. atlanis and M. bivittatus. 'The worms seem to leave the bodies of the grasshoppers when these insects are maturing. We had not the opportunity to observe grasshoppers in the early stages of parasitism, but in August and September dissection of a large number of the insects sshhowed that the worms were located within the body cavity. Later in the season, when the worms are about to emerge, the grasshoppers fall over on one side, kick for a time and then die. In the meantime, the worms gradually bore their way through the body wall and reach the exterior after which they make their way slowly into the earth. Usually only one worm parasitizes a grasshopper, but by dissection we have often found two or three and in one case we found forty. Needless to say, that when an insect contains so many worms the abdomen is considerably ‘swollen.
The length of these female worms varied from two to eight inches. It is extraordinary that with hundreds of hoppers dying everywhere, we were unable to find any males.
A great many nematodes, at one stage of their life cycle, seek water on leaving their hosts and there mature, or wait until another host presents himself. We placed about two dozen of our worms in a bowl of water in which they seemed to flourish for about two weeks. However, the localities where the hoppers, and conse- ‘quently the worms abounded were free from streams, ponds or marshes of any kind. The Connecticut River flows through a val- ley at a distance of about one-half mile so it seemed unlikely that the worms would travel sofar. In all probability, we thought, the worms make their way into the soil on leaving the insects and this we found true. We placed recently dead parasitized hoppers in boxes containing earth. In about three days the boxes were ex- amined and the worms were found coiled up at a depth of about one foot. Often a number would be coiled up together in one
14 Psyche [February
spot. An examination of the soil in the fields revealed quantities. of the worms below the surface at a distance of six inches to one foot. November the 7th and 8th, long after the grasshopper sea- son, the ground now cold was again broken and the nematodes. were found coiled up at about the same distance below the surface. Undoubtedly they hibernate in these positions.
During the highest mortality we made a series of dissections in order to determine the per cent. of parasitism. On a place called the Halladay Farm, we obtained the following astonishing high: figures by the dissection of M. bivittatus.
Sept. 8. .10092 92 dissected and worms found in 59%.
105? )B0G oni Bn eee ct Se Ba Ea Rte ne ohne ae EB AD ligh pain aries “Stare <0) 0c ay yan ees ve 6 66 Oar S18 Otte oe er a 6) aa
On a place called the Tarbox Farm, we dissected about equal numbers of M. bivittatus and M. atlanis and obtained the following:
Sept. 8. 1009 2 dissected and worms found in 22%.
= ATOR Mio me zc 3 oo eee “- 12. 60:9°¢ * ¥ a Ce ee Bre. Os 2 5: 7 SS as “S102, S01) 3 . ; lee Oe LOW et "4 ey en Sp
In both series of dissections it will be noticed that the percentage: of parasitism in females is much higher than in males. Since the life-history of the worm is still so obscure we are at present unable to offer any explanation for this fact.
How the grasshoppers become infected is unknown. Since the nematodes are so large when they leave the grasshoppers in order to burrow into the soil, we are under the impression that grass- hoppers are the secondary hosts. It is difficult to imagine what animal might constitute the primary host. Perhaps some other insect may furnish the clue to this interesting question.
Next summer we hope to extend our observations and attempt to gain a more complete insight into the life-history of this Mermis parasite. Some parasites fluctuate so numerically from one season:
1918] Richardson—Pulsatile Vessels in Legs of Aphidide 15
to another, that an entirely different condition may, of course, present itself in 1918. We mean that the worms may not be so plentiful for some reason and if this should prove true, it will be difficult to obtain very much information.
From our observations this summer (1917) we firmly believe that the nematodes accomplished an immense reduction in the number of grasshoppers near Dummerston Station, Vermont. This worm, if its life-history is investigated, might offer possibilities for introduction into regions where it does not occur and where grasshoppers are a pest. For this reason, and because we were unable to find any records of such a high degree of parasitism, we thought it best to present these preliminary observations.
THE PULSATILE VESSELS IN THE LEGS OF APHIDID.
By Cuas. H. Ricwarpson,
College of Physicians and Surgeons, Columbia University, New York City.
When one of the light-colored aphids, like Myzus persice Sulz.,