290 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



constituent substances, and this, it is thought is due to the more 

 complete coating effected by the mixture because of its better flowing 

 qualities. The one to five mixture is equally as good as the one to 

 one and much less expensive. 



The increase in crop obtained by the applications is about 200 per 

 cent. In the other tests the increase ranged from barely perceptible 

 when the bud cutting on the check was low to more than 100 per 

 cent when it was high. 



The returns at Cologne, while larger than those obtained elsewhere, 

 are due to the maintenance of a more complete coating of the buds 

 during the critical period, and should be susceptible of being dupli- 

 cated or bettered when sufficient care and intelligence are employed. 



LITTLE KNOWN WESTERN PLANT LICE. U 



By W. M. Davidson, U. S. Bureau of Entomology, Walnut Creek, Cal.^ 



Vacuna drijophila Schrank (?). Figs. 16, 1 to 3. 

 Chaitophorus sp. Davidson, Jour. Econ. Ent., Feb., 1914, p. 128. 



The apterous vivipara (erroneously thought at the time to be the 

 stem mother) and young sexual were described by me in 1914 under the 

 name of Chaitophorus sp., the young sexual somewhat resembling the 

 spinous dimorphic forms found in the Chaitophorincc in species Uving 

 on maple and box elder. However, after other forms had been en- 

 countered it became obvious that the species was widely separated 

 from Chaitophorus, and that it belonged to a small group in which the 

 sexes are small and wingless and in which the true female deposits 

 normally but one winter egg. In their sexual characteristics the 

 Vacunina approach the Schizoneurina; and Pemphigince but the habits 

 of the other forms more nearly approach those of the Chaitophorince 

 and the Lachnina. 



In the species with which we are concerned the stem mothers hatch 

 about the beginning of March, at a time when the buds of the oak have 

 not perceptibly swollen. The lice feed at the base of a bud and are 

 at first dark olive green with erect white spines-. As they grow they 

 become darker and mature individuals are brown. They remain at the 

 base of the bud and produce a generation of young which become 

 apterous viviparje and in turn give birth to the third generation. Some 

 of the third generation become nymphs and later acquire wings. The 

 second and third generation apterse are bright green with antennae 

 and legs pale hyaline greenish white. The pupae are similar in color 



'Published with the permission of the Chief of the Bureau of Entomology. / 



