1M9] ECONOMIC ZOOLOGY- ENTOMOLOGY. 455 



The results of spraying testa made by the author Indicate that glue must be 

 added to the oil emulsion when it Is being made, whereas it can be added 

 afterwards to a mlsdble <>ii. with a view to determining the effect upon 

 white iiy and purple scale, applications were made on Augusl 18 in wliich 

 mlsclble oil was stabilized (1) with glue solution and (2) with milk powder. 

 a stabilized emulsion was also used in place of the mlsclble oil, and the glue 

 solution was used for a binder. It was found later that the addition of glue 

 to a stabilized emulsion was unnecessary. White fly pups were killed per- 

 fectly, and the sooty mold was loosened and fell off after the first rain. At 

 the time Of writing the sprayed trees were free from sooty mold and purple 

 scale and had a much better appearance than a check row of unsprayed irees 

 in the same grove. It is pointed out that while the mixture seems to be 

 satisfactory as an insecticide it may injure the trees and fruit. 



"There is no evidence to show that the combination of oil emulsions and 

 [ime-8Ulphur is superior to the combination of the emulsion and the soda 

 sulphur solutions. So, until further knowledge has been obtained, it would be 

 well to try the former combination only experimentally." 



The toxic action of KCN and its relation to the state of nutrition and age 

 of the cell as shown by Paramecium and Didinium, BABBASA L. Lund (Biol. 

 Hiil. Mar. Biol. Lab. Wood* Hole, 35 (1918), No. .',. pp. 21 t-281, figs. 3). A re- 

 port of studies of the comparative resistance of Paramecium and Didinium 

 to the toxic action of potassium cyanid in culture medium, and the factors 

 responsible for the observed differences among Individuals living in the same 

 medium. 



The tarnished plant bug and its injury to nursery stock, L. HA8EMAN 

 (Missouri Sta. Research It ul. 29 (1918), pp. 3-20. pis. G) .— This is a report of 

 Investigations of Lygus pratensis, of which insect an earlier account has been 

 noted (E. S. R., 29, p. 354). The author's conclusions, based upon the investi- 

 gations here reported, are as follows: 



"The typical injury to nursery stock, known as 'stop back,' ' bush head.' or 

 'bunch-head' in Missouri is the result of feeding by the tarnished plant bug. 

 This injury baa been common in the State for years, out has attracted special 

 attention only in the last seven years. 



"The main injury is done by the adults which pass the winter. Some of the 

 late work may be done by adults maturing in the summer. The nymphs do not 

 breed and feed on nursery stock. The principal injury is done in the spring 

 before the dormant buds have produced a growth of more than 11' in. Later 

 injury does occur but it is usually of little importance. Teach, pear, and 

 cherry are most severely attacked in Missouri. 



"The pest hibernates in the adult stage between the leaves of mullen and 

 similar plants, under rubbish, leaves, and other shelter. Only a small per- 

 centage of the adults which hibernate live through the winter. The bugs are 

 strong tliers, but collect in greatest abundance and do most damage on nursery 

 stock near favorable breeding and hibernating places. 



"In the development of the pest it passes through five nymphal stages. rno 

 second of which can not be distinguished with certainty without actually 

 following the hourly growth and development of the nymph from the time it 

 hatches. 



"The pest oviposits largely in the blossoms of composltS and nymphs feed 

 on the sap of the same plants. 'Mare's tail' [Brigenm rniiarlcvsis) is pre- 

 ferred, although the pest breeds on a variety of other plants. 



"In the control of the pest, clean culture to destroy plants on which It 

 breeds, and the destruction of favorable hibernating quarters are essential 

 112874°— 19 5 



