347 



FuLLAWAY (D. T.). The Melon Fly— Its Control in Hawaii by a 

 Parasite introduced trom India. — Hawaiian Forester & Atjricul- 

 turisf, Honoluhi, xvii, no. 4, April 1920, pp. 101-105. 



The bulk of the information contained in this paper has already 

 been noticed [R.A.E., A, v, 2, etc.]. Opius fletcheri now accounts for 

 the destruction of 50 per cent, of the melon-fly, Dacus (Bactrocera) 

 cucnrbitae, infesting fruit in Hawaii, and in some localities it is again 

 possible to grow melons successfully. 



Gahan (A. B.). Black Grain-stem Sawfiy of Europe in the United 

 States.— U.S. Dept. Agric, Washington, B.C., Bull. 834, 19th 

 May 1920, 18 pp., 2 plates, 1 fig. 



Trachehis tabidus, F. (black grain-stem saw-fly of Europe) has 

 evidently been established in America for some years, though how it 

 was introduced there is unknown. Its present distribution is confined 

 to some half-dozen of the eastern and central States, but the species, 

 judging from its expansion in Russia, may eventually spread from 

 coast to coast in America. The only known food-plants in America 

 are wheat and. very occasionally, rye. A description is given of the 

 various stages of T. tabidus, with a key for separating the grain- 

 infesting sawflies, T. tabidus, Cephus pygmaeus, L., and C. cinctus, Nort. 

 The life- histories of T. tabidus and C. cinctus are probably similar. 

 Oviposition of the former species occurs from 15th May to 10th June, 

 the eggs being inserted in a sht in the stem made by the female at 

 some distance above the ground. The young larvae burrow down- 

 ward through the pith of the stem, hollowing it out to the base. The 

 larvae become mature about the time that the grain is ripe ; by 22nd 

 July during the season investigated all were full-grown and had 

 evidently gone into hibernation at the extreme base of the stem, 

 where they were encased in a silken tube or lining in a burrow entirely 

 filhng the hollow straw and closed above by a wad of frass. Before 

 closing the burrow the larva almost completely severs the stem from 

 the inside, the cut being at or near the surface of the ground and usually 

 a httle above the first node on the stem where the surface roots put 

 out. Just enough of the epidermis is left to prevent severing the straw 

 and to allow it to stand erect, so that the first shght bending of the stem, 

 as by a strong wind, causes it to snap oft* and fall. Both the end of the 

 stalk remaining in the ground and the fallen straw are distinctly 

 concave or funnel-shaped, clearly defining the work of the pest. The 

 hibernating larva remains in the stub of the wheat stalk left in the 

 ground, where it fives from about the time the wheat is ripe until some 

 time in the following spring when it pupates, probably in late April 

 or early May. Under some conditions the fife-cycle may be extended 

 over two years ; this is probably unusual, but shows a high degree of 

 adaptability on the part of the species for overcoming unfavourable 

 conditions. Some of the infested stems are able to develop at least 

 partially filled heads and the extent of loss will probably depend in 

 some degree upon weather conditions during the period of ripening of 

 the grain. 



Neither of the parasites of this species occurring in Russia [R.A.E., A, 

 iv, 21] has been found in America, but an evidently important parasite 



