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A Revision of the Genus Locusta, L. (= Pachytylus, Fieb.), with a New Theory as to the Periodicity and Migrations of Locusts

Published online by Cambridge University Press:  10 July 2009

B. P. Uvarov
B. P. Uvarov
Affiliation:
Assistant Entomologist, Imperial Bureau of Entomology
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Extract

The genus Locusta, L. (= Pachytylus, Fieb.) includes two of the most destructive swarming locusts of the Old World: the widely distributed L. migratoria, L. (with L. danica, L., and L. migratorioides, Rch. & Frm., as its forms; see below), and the South African L. pardalina, Walk. The literature on the economics, biology and especially on the means of control of these locusts is enormously extensive, but at the same time their systematic arrangement is in considerable confusion, and extremely contradictory opinions as to the mutual relationship of the different so-called species exist among specialists. As a direct consequence of this, the field research and control work of economic entomologists is apt to suffer through the difficulty in getting a particular species properly named, and thus it is often impossible to make a comparison of the records as to the biology and control of the same species in different countries.

Type
Original Articles
Information
Bulletin of Entomological Research , Volume 12 , Issue 2 , June 1921 , pp. 135 - 163
Copyright
Copyright © Cambridge University Press 1921

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References

page 135 note * See, for instance, the interesting paper on the biology and control of the Malayan locust by H.C. Pratt (Bull. No. 27, Dept. Agric. Fed. Malay States, 1915), who states that “many attempts to identify this Malayan locust have been made and correspondence has been entered into with authorities throughout the world, but without success.” He has been compelled to call the insect, simply, Pachytylus sp.

page 137 note * I am much indebted to Mr. J. H. Durrant for the help he has generously given me in the solution of this question.

page 137 note † I must candidly confess that when starting my work I had only a very modest intention—to find out characters for separating migratoria and danica, which I assumed beforehand to be distinct specifically. The facts quickly destroyed my preconceived opinion and compelled me to work deductively.

page 137 note ‡ This important and rather striking difference between migratoria and danica was first noted by the artist of the Zoological Museum in Petrograd, Miss O.M. Somina, who made drawings of both insects for Mr. I. Shevyrev; and the latter drew my attention to it.

page 142 note * I do not propose to give a detailed description of the larval stages of migratoria, since this has been done more then once by different authors; very good descriptions and fairly good coloured figures have been given by H. C. Pratt (Dept. of Agric. Feder. Malay States, Bull. No. 24, 1915).

page 143 note * This fact was first observed by my assistant, Mr. Th. Gliniuk, in 1912, in Stavropol province, and was recorded by me in the paper: “The Fight against Locusts in the Government of Stavropol in the years 1907’1912,” St. Petersburg, 1913 (in Russian).

page 143 note † The matter is really more complicated than this, since the selection of spots for oviposition is usually closely connected with the more minute character of the soil and vegetation.

page 144 note * I intentionally avoid discussing here the question of the direction of movements and its causes, since it is very complicated, and besides, it has no direct connection with the chief problem we are now investigating; one point, however, is worth mentioning: that the direction of movement has, as a rule, nothing to do with the looking for food, since, for one thing, larvae do not feed during the day, and they often move from fertile spots into entirely barren places.

page 144 note † This kind of tropism is not uncommon among other insects, and even vertebrates; a herd of cattle will afford excellent examples of it.

page 145 note * The habits of the larval swarms of migratoria are well known to those concerned with locust control in Russia, and as the insects are now almost exclusively destroyed by spraying with arsenical insecticides, which are of use only when the actual food of the larvae is poisoned before feeding, no spraying is done during day, when swarms are in movement. The daily work is usually divided into two periods, and spraying is done in the early morning, before the larvae begin to go down from the plants, and in the evening; the evening work begins before the swarms stop for the night, since it is always easy to reckon where a certain swarm will stop, and the spraying is continued till it is quite dark; this evening spraying is the more effective. In cool weather, when swarms do not move, work goes on all day continuously.

page 147 note * This is directly due to the fact that most entomologists have regarded danica as distinct from migratoria and as being an entirely harmless species, so that the study of its habits has been neglected.

page 148 note * Report on the work of the Turkestan Entomological Station in 1912, 1913, 1914, and part of 1915; pp. 28, 55’59; Tashkent, 1915 (in Russian); see also Rev. Appl. Entom., iv, p. 211.

page 150 note * A permanent breeding region of L. migratoria.— B. U.

page 151 note * Die Afrikanischen Wanderheuschrecken.— Beith. zum Tropenpflanzer, xi, No. 2, 1910, p. 82, footnote 22.Google Scholar

page 151 note † Die Wanderheuschrecken und ihre Bekämpfung in unseren Afrikanischen Kolonien. Berlin, 1902.

page 152 note * I have recorded (Revue Russe d’ Entom., xiv, 1914, p. 232) this form from the Pamir upland as high up as 11,000 ft. above sea-level; there is in the British Museum a couple of specimens taken at Giangtse, Tibet, at an altitude of 13,000 ft.

page 152 note ** Dr. J. Rehn, of Philadelphia, informed me recently that he is of the same opinion.

page 152 note † Abh. Senkenberg. Naturf. Ges., xxiv, pp. 194, 196.

page 153 note * Die taxonomischen Grenzen der Art und ihrer Unterabteilungen. Berlin, 1910.

page 154 note * Horae Soc. Entom. Ross, xl, No. 3 1912.

page 155 note * The direct cause of this ignorance is that injurious insects, and locusts especially, are studied only in the years of maximum dévelopment, and nobody cares about them in the minimum years, when the clue to the whole locust problem is most likely to be found.

page 159 note * It is extremely interesting to note here that the larvae of most swarming and migratory locusts (Schistocerca peregrina, OI., Dociostaurus maroccanus, Thb etc). Present the same general type of coloration in black and reddish, or yellow, forming a very striking design. This phenomenon is well worth further investigation.

page 161 note * It is quite obvious that the exact determination of the phases is possible only in the case of typical specimens and not of intermediate examples; the most reliable results can be obtained only from examination of large series.

page 163 note * The terminologym of the parts of the genitalia adopted here is that of L. Chopard (Recherches sur la conformation et le development des derniers segments abodominaux chez les Orthoptères.— Thèses présentées a la Faculte de Sciences de Paris; Serie A, No. 847, 1920).

page 163 note ‡ See the footnote on page 161.