ECONOMIC ZOOLOGY — EISTTOMOLOGY. 657 



structiou was caused almost wholly by 3 native species, namely, the two- 

 striped locust {Melanoplus vivitattus), the red-legged locust (M. femur-ru- 

 brum), and the lesser migratory locust (M. atlantis). 



Papers on insects injurious to citrus and other subtropical fruits. — The 

 orange thrips: A report of progress for the years 1909 and 1910, P, R. 

 Jones and J. R. Horton (U. 8. Dept. Agr., But: Ent. Bui. 99, pi. 1, pp. 16, pis. 3, 

 figs. 2). — This is a report of studies of the orange thrips (Euthrips citri) in 

 continuation of those of Moulton previously noted (E. S. R., 20, p. 956). 



This species is thought to be a native of the Sierra Nevada foothills or the 

 adjoining plains of the southern San Joaquin Valley. It is distributed through- 

 out the entire orange belt of the San Joaquin Valley and has been collected in 

 several places in Southern California and at Phoenix, Ariz., by the senior 

 author. The infestation in Arizona embraces orange groves in the Salt River 

 Valley surrounding Phoenix. It has also been reported from Hermosillo, 

 Sonora Province, Mexico. Attention Is called to the fact that While E. occir 

 dentaUs also is occasionally found upon citrus trees, as reported by Coit (E. S. 

 R., 21, p. 44), it rarely causes serious injury. 



In addition to citrus, the authors have taken the orange thrips from pome- 

 granate (Punica gramatum), varieties of European grape, California pepper 

 tree (Schinus inolle), umbrella tree, pear, apricot, peach, varieties of European 

 plum, willow (Salix sp.), dock {Rumex sp.), purslane {Portulaca oleracea), 

 olive, red raspberry, rose, and Solanum sp. 



Technical descriptions are given of the egg, larva, and pupa. The orange 

 thrips passes the winter in the adult state, and it is generally the adult form 

 which first becomes conspicuous upon the orange trees in the spring. Examina- 

 tions for eggs revealed the fact that most of them are placed in the new, tender 

 growth, being inserted into both upper and lower leaf surfaces and also in the 

 shoots. They are also placed in the receptacles of the blossoms after the petals 

 have fallen and in young fruit and fruit stems. The relative abundance of the 

 thrips on various food plants during the season is diagrammatically illus- 

 trated. The life cycle obtained by adding the average lengths of egg, larval, 

 and pupal stages and allowing 3 days for the preoviposition period was found to 

 be 18.08 days from May to August, 1909, while for the months from April to 

 August, 1910, the period was 23 days. "Although the number of generations in 

 a season has not been definitely observed, there are probably 4 and a partial 

 fifth during the period of May to July, inclusive, and 1 generation in each of 

 the months of March, April, August, September, and October, making in all a 

 possibility of 8 to 10 generations for the season." Its ability to run, leap, and 

 fly is much greater than that of any other thrips so far observed by the authors, 

 who have frequently seen adults fly from one tree to another 20 ft. or more 

 distant. 



The spraying experiments here reported show that the pest can be controlled 

 by 4 sprayings of lime-sulphur solution combined with a commercial tobacco 

 extract, which should be applied when the thrips become sufficiently numerous. 

 Three applications should be made in the spring months to save the fruit and 

 spring growths from injury, and one in the fall to lessen the feeding injury to 

 the fall growth of the orange trees. The 3 spring applications should be made 

 as follows: The first just after most of the petals have fallen; the second, from 

 10 to 14 days after the first; and the third, from 3 to 4 weeks from the time 

 of the second treatment. The spraying solution should consist of lime-sulphur 

 (33° B.) 1:75 and blackleaf tobacco extract (2f per cent nicotin) 1:100; or, 

 using blackleaf "40" (40 per cent nicotin) tobacco extract 1:1,800. If lime- 

 sulphur of 36° B. is used, the formula would be lime-sulphur 1 : 86 and black- 

 leaf tobacco extract 1 : 100 ; or blackleaf tobacco extract " 40 " (40 per cent 



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