135 



A REVISION OF THE GENUS LOCUSTA, L. (= PACHYTYLUS. FIEB.). 

 WITH A NEW THEORY AS TO THE PERIODICITY AND MIGRATIONS 



OF LOCUSTS. 



By B. P. UvARo^•, F.E.S., 



Assistant Entomologist, Imperial Bureau of Entomology. 



Contents. 



I. Introductory. . 



II. On the generic name Locusta, L. 



III. Locusta migratoria, L., and its forms . . 



IV. Locustana pardalina, Walk., and its phases 

 V. Systematic part 



I. Introductory. 



PAGE. 



135 

 136 

 137 



155 

 159 



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. migrator ioides, Rch. & Frm., as its forms ; see below), and the 

 South African L. pardalina, W^alk. 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. 



Having had the opportunity of conducting, during the years 1911-14, extensive 

 field research work and control work on L. migratoria in the northern Caucasus 

 (Russia), and being a systematist, I could not fail to see at once that only very little 

 progress could be made without a definite solution of the question of the inter- 

 relation between L. migratoria and L. danica, which latter has been accepted 

 by many authors as a species distinct from migratoria, and as conspecific with it, 

 by others. The same question arose before the Turkestan Entomological Station 

 (in Tashkent) as soon as its staff began to work on L. migratoria. 



Apart from my field work, which involved the study of immense series of living 

 specimens in all stages, I endeavoured to gather all reliable information as to the 

 distribution and local, individual and annual variability of L. migratoria and danica 

 in different parts of their range, and owing to the support of entomologists and 

 institutions throughout Russia and elsewhere, I managed to concentrate in my 

 hands extremely rich materials from the following sources : Turkestan Entomological 

 Station (V. j. Plotnikov) ; Astrakhan Entomological Station (N. L. Sakharov) ; 

 Natural History Museum in Kherson (J. K. Pachossky) ; Zoological Museum of the 

 Moscow University (Prof. J. Kozhevnikov) ; Caucasian ]\Iuseum in Tiflis ; Zoological 

 Museum in Berlin. The following persons also contributed very valuable materials 

 and information : Prof. J. Shtchelkanovzev, E. Jatzentkovsky, V. Artsimovicz 



* 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. 



