970 EXPERIMENT STATION RECORD. 



Viiselin, lanolin, and allyl sulphid, 1 per cout; tar water, eucalyptus, and 

 kuinnud, l<i per cent. 



The " silver top " condition of meado-w grasses in Finland, E. 

 Reuter (Acta aSV^c". Fauna et Fbyra Feimlca^ 19 {1900), X<>. Lj>p. 1S6^ 

 pis. 2). — This article is in the nature of a monographic account of the 

 insect attacks which result in the blasting of the heads of grasses. The 

 author's observations are confined chiefl}^ to Plileum prate iixi and 

 Al<>pe(-urHx pratensls. An elaborate classification is giv(in of the insect 

 attacks which cause these conditions, the classification being ))ased on 

 the method of attack and upon the part of the plant attacked. The 

 author gives a review of previous investigations on this su)>ject in other 

 countries, together with notes on the grasses affected and on the insects 

 which cause the damage. Among the insects which are responsible 

 for the silver top condition in Finland may be mentioned TIadena 

 secalis^ H. strigilis^ Tortrlxpaleana^ Pedlculoide><, granvi 711011^ AptlnotJi- 

 rips rufa^ and Tarsonenms culmicolus. The last-named species and 

 Pediouloides graminuni are described as new. P. grarninum was found 

 to be very destructive to grasses. Pregnant females of this species 

 were first found in the middle of July on Phleum prraten-se. From this 

 time until fall such individuals were found in considerable numbers, 

 especially on Agropyram repent. These females attach themselves to 

 the stems of grasses and remain so attached until their death. The 

 author made numerous observations on the relative numbers of the two 

 sexes of this species, and found that there appeared to be no males dur- 

 ing the first half of the summer and that during the second half of the 

 summer the}" were comparatively rare. From observations made in 

 the field and laborator}^ the author believes there are two complete 

 generations of this insect annually. Besides the species already men- 

 tioned, the author gives notes on a numl)er of others which are of less 

 importance in causing the silver top condition. The complete list as 

 studied by the author includes 4 species of Thysanoptera, 5 of Lepidop- 

 tera, 6 of Diptera, 2 of Hymenoptera, 1 of Hemiptera, and \ species of 

 mites. An extended bibliography is given of the literature relating to 

 ' this su])j('ct. 



The stra-wberry-root louse; the destructive pea louse in Dela- 

 ■ware, E. D. Sanderson {Belauiare Sta. Bid. JjB., pp. '2Jf.,Jigs. 7). — The 

 author gives notes on the habits and life histor}' of Aphis forbesi, and 

 describes the preventive remedies which have given best success in 

 combating this insect. Among such remedies mention may be made 

 of the use of uninfested plants, rotation of crops, and disinfection of 

 strawl)erry plants by dipping in kerosene emulsion or tobacco water, 

 or by fumigation with hydrocyanic-acid gas. 



Notes are given on the occurrence of the destructive pea louse in 

 Delaware. Its preferred food plant is said to be crimson clover. An 

 experiment was tried in spring on an acre of infested peas with a 



