567 



organisms capable of passing through diatomaceous filters. In a 

 large series of passage infections 25 caterpillars of the gipsy moth 

 \Lymantria dispar] were infected at a dilution of 1 : 1 ,000 with material 

 ■obtained from a caterpillar previously dead of wilt. All these cater- 

 pillars died of typical wilt within 2 or 3 weeks, while 25 other 

 caterpillars fed with the sterilised filtrate hved, pupated, and trans- 

 formed into moths. Second, third and fourth passage infections were 

 performed and the results were similar, except that the period from 

 infection to death was considerably shorter at the fourth passage 

 than at the first three, this shortening of time seeming to point to an 

 increase in virulence with successive passages. Comparison of these 

 results with those of other workers on the 32 or 33 disease-causing 

 filterable viruses known, leads to the conclusion that the organism 

 of wilt disease is a parasitic ultra- microscopic form, the nature of which, 

 whether animal or vegetable, is not at present known. 



Marlatt (C. L.). The Origin of the Pink Bollworm. — Science, 

 Lancaster, Pa., xlviii, no. 1239, 27th September 1918, pp. 309-312. 



The determination of the original habitat of Pectinophora gossypiella, 

 Saunders (pink bollworm) is of great interest in relation to the present 

 distribution of this insect, and may be of importance later, as indicating 

 where parasitic or other natural checks may be found. 



Examination of the records strongly supports the theory that the 

 insect originated in Southern Asia, probably India. The material 

 from which the original descriptions were made by Saunders in 1842, 

 was sent by the superintendent of the Government Cotton Plantations 

 at Broach (Baruch) in Western India, accompanied by the information 

 that it was very destructive to American cotton growTi on light alluvial 

 soil, but that the cotton on the black soil was not touched by it. He 

 added that native cotton was sometimes affected by it, thus implying 

 that it was a known but comparatively unimportant enemy of such 

 cotton in India prior to 1842. The hardy and rather unproductive 

 cottons of India and other southern Asiatic countries, probably 

 long associated with this insect, evidently were then, and are still, 

 fairly resistant to its attacks ; while the introduced American and 

 Egyptian varieties, being less so, furnish exceptional breeding condi- 

 tions and are much more seriously attacked, thus bringing into 

 prominence an insect which had previously been for the most part 

 overlooked. Saunders at the time made no suggestion that the insect 

 was other than a native Indian species, or that it was imported with 

 the American cotton. 



Support for a theory of possible American or at least African origin 

 is based on the fact that the only near relative of the pink bollworm, 

 P. malvella, Z. , is known from Africa as well as southern Europe ; 

 but this is an unimportant point, since more accurate knowledge 

 ■of the distribution of this species may show it to have a more extended 

 range throughout southern Asia. Again, it may be urged against 

 the view that this insect is of African origin that records, most of 

 them antedating from 8 to 70 years the first report of its occurrence 

 in Egypt, indicate its wide distribution throughout southern Asia, 

 including Ceylon, India, Burma, Straits Settlements, Philippines, 

 •Japan (?) and Hawaii. The record of the cotton crop in Egypt up to 



