1064 INSECTS ETC. INJURIOI'S TO VARIOUS CROPS 



2) Spraying on the youngest, which are the easiest to get at, arsenate 

 of sodium and quicklime, which safeguards the plants against further at- 

 tacks (arsenate of sodium, 10.3 to 12.2 oz ; quicklime, 2.2 lbs ; water 22 

 galls.) ; 



3) Coating the pine trunks over a more or less extensive area with 

 a sticky pitch substance. The larvae coming down from the tree and those 

 climbing up in search of food stop in front of the coated belt and can easily 

 be destroyed. This is a very practical and easy method of control. 



839 - Lyda hypotrophica, a Hymenopterous Pest of Epicea in the Forests of 



Roggenburg, Germany. — Parts in Zeitschrift fur ani^i'wandti' EntomoloL^tc, Vol. 3, Xo. i, 

 pp. 75-96. Berlin, March lyiC. 



A very detailed description is given of the occurrence of Lyda hypo- 

 trophica Htg. (= Cephaleia abietis L'.) in the forest of Roggenburg (vSuabia) 

 and the damage it has occasioned of recent years. These data are based 

 on observations made in the Royal' Forest District of Breitenthal, but 

 they are so characteristic that they may be considered as being likewise 

 typical for the whole of Suabia. 



In August 1911, inastand of epicea 119 years old, in the .southeast part 

 of the said f 01 est, many trees were remarked with their tops and side bran- 

 ches entirely stripped cf needles. This fact was at first put down to the 

 excessively dry weather in that year, but on felling S'ome trees later, it 

 was found to be caused by injury due to Lyda hypotrophica. In the month 

 of vSeptember following, all the stands attacked where the insect was likely 

 to be sheltered were studied, and the quantity of larvae contained in the 

 soil was determined in 323 plots of i square metre each distributed over 

 different points. It was found, in accordance with the literature of the 

 subject, that stands of 60 to 120 years had suffered most, both with regard 

 to infested area and number of larvae. 



The chief object of these experiments was to determine how widespread 

 was the occurrence of the insect in the forest. As however the majority 

 of the larvae generally live in that part of the soil which is shaded bj' the 

 largest trees, the latter were almost exclusively used for the experiments. 

 The result is that this method only supplies maximum figures as to the pre- 

 sence of the larvae. 



\Vhen in 1912 the Writer took over the management of the forest dis- 

 trict of Breitenthal, he hastened to obtain average figures as to the presence 

 of larvae in the soil. He not only selected the plots in all parts of the 

 forest, but he more than trebled their number. This was the more necessar}*, 

 inasmuch as the first experiments had exhibited great variations in the num- 

 ber of larvae, even per unit of shaded area. There had been found in one 

 district 2083 larvae per square metre of shaded area, while in another the 

 number was only 480. 



These experiments have shown that no stand throughout the total 

 extent of the Royal forest district comprising 5683 acres was free from 

 larvae, independently of the age of the trees. One stand alone showed an 

 increase in the average number as compared with 191 1 ; generally this num- 



