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AViLLiAMS (C. B.). The Pea Thrips {Kakothrips robustus) — Ann. App. 

 Biol, London, i, nos. 3 & 4, January 1915, pp. 222-246, 12 figs. 



In an account of the history of K. robustus, it is stated that the damage 

 to peas in Germany, described by Kirchner in 1890 as due to Thrips 

 erealimn, was in reahty due to the former species. The synonomy 

 of this species is discussed and it appears that Thrips pisivora, Westw., 

 T. physapus, von SchiUing, Physopus robusta, Uzel, Eulhrips robusta, 

 Bagnall, and FrankUnieUa robusta, WilUams, are all synonyms of 

 K. robustus. Detailed descriptions of all stages in the life-history are 

 given, as well as a list of recorded localities in England, Wales, and 

 Ireland. There is no record of its occurrence in Scotland, but in 

 Europe it occurs in Bohemia, France, Germany, Italy and Sweden. 

 The adults, the habits of which are given in detail, appear from May 

 to August, the males only occurring in the earlier part of this period. 

 The eggs, which hatch in about 9 days, are laid chiefly in the tissue 

 of the stamen sheath. There is one larval moult, and the second 

 stage, when full fed (about 24 days from oviposition), descends into 

 the ground to a depth of from three to twelve inches. Here the mature 

 larva remains till the following spring, when the two pupal stages are 

 passed through and the adult emerges. There is only one brood each year. 



The parts of the plant which suffer most from the ravages of this 

 insect are the young leaves in the terminal shoots, the flowers, and 

 the pods ; there is no record of the older leaves being attacked. In 

 England, the terminal shoots appear to be infested only when other 

 situations are not available, as in the case of a very early attack in 

 May, before the flowers are out, or later in the year on late sown 

 varieties. When the flowers are attacked, they shrivel up and turn 

 brown, and in cases of severe attack no pod at all may be formed. 

 The damage is generally most noticeable when the pods are small ; they 

 are then undersized, deformed and covered with characteristic silvery- 

 brown areas where the larvae have been feeding, due to the presence 

 of air in the outer cell layers of the plant introduced by the sucking 

 action of the larvae. The damage may be very extensive and 

 occasionally the whole crop is spoiled. K. robustus seems to confine 

 itself chiefly to the edible pea {Pisum sativum) and the broad bean 

 (Vicia fabu) and their varieties. Both field and garden crops are 

 attacked, but the latter seem to suffer most. This may be due to the 

 fact that in fields there is usually a rotation of crops, while in gardens 

 the same crop is often grown on the same plot, or close to it, year 

 after year. The author has not yet found this species on either sweet 

 peas [Lathyrus odoratus) or scarlet runner beans {Phasenlus vulgaris), 

 though these are host-plants in France. Thrips are often abundant 

 on both plants, especially the latter, but, in the author's experience, 

 always belong to other species, chiefly Franklinielh intonosa, T. tabaci, 

 T. validus, or Physothrips atratus. When damage is recorded on runner 

 beans, it is thought to be due to one or more of these species and not 

 to K. robustus. The author has also found this species on flowers of 

 knapweed {Centaurea nigra), and it has been taken both in Bohemia 

 and Britain in flowers of Scabiosa arvensis [field scabious or clod-weedl. 

 Medicago sativa., Cijuga reptans, Ecbalium elaterium, and Coronillu 

 vulgaris have all been recorded as food-plants in France, but the last 

 two do not occur in Britain. A few notes are given of other 

 Aeolothripid.\e and Thripidae found on peas and beans. 



