664 EXPERIMENT STATIOIT RECORD. [Vol. 41 



driving rains and sleet storms are important factors in the natural control at 

 this time of the year. 



" Under average conditions, M. solanifolii is found associated vpith R. persiccB 

 on spinach, but the former species is more numerous and widely distributed in 

 the fields. Dispersal from plant to plant and field to field is accomplished by 

 both the alate and apterous forms. The latter have been observed to travel 

 several yards in order to reach a fresh food plant. The rate of infestation may 

 be very rapid. In 1918 a 15-acre field of potatoes had 97 per cent of the plants 

 infested within a period of 15 days. Other crops are likewise infested very 

 rapidly. 



" It has been observed that early maturing varieties of potatoes were the first 

 to be infested in the spring, and suffer more serious injuries than do later ma- 

 turing varieties. A variety of spinach has been obtained from Manchuria which 

 is apparently distasteful to the aphids ; at least, it is infested only when other 

 food is scarce, or the aphids are extremely abundant. This strain is being 

 used as the basis in our breeding experiments to obtain a blight-resistant strain. 

 Fi and F2 hybrids of this strain are showing this character to a certain extent. 



" Generation experiments were conducted from 1915 to 1918. Nineteen first 

 born and eight last born generations, or an average of 13* generations, were ob- 

 tained between May 1 and November 20, 1915. Thirty-four consecutive first 

 born generations were obtained between April 1, 1916, and April 1, 1917. The 

 average age at which females gave birth to young was 10.9 days in 1915 and 



11.1 days in 1916. The females mature at an earlier age during the summer 

 than at other seasons of' the year. The number of young born per day was 

 found to vary, 12 being the maximum obtained. The maximum number of 

 young produced during the life of a single female was 87. The averages were 

 43.3 in 1915 and 46.7 in 1916. The average life of a viviparous female was 



29.2 days in 1915 and 32.6 days in 1916. The length of the reproduction period 

 averaged 17.96 days in 1915 and 18.9 days in 1916. M. solanifolii molt four 

 times; the average length of the instars was as follows: First, 54i hours; 

 second, 65i hours ; third, 69i hours ; fourth, 65§ hours. 



"Two internal parasites of this aphid have been reared. Aphidius polygona- 

 phis is most abundant; Diaretus rapea parasitizes this species occasionally. 

 The common aphid fungus Empusa aphidis is one of the most important enemies 

 of this aphid during the warm, humid periods of July and August. The two 

 ladybird beetles Hippodamia convergcns and Megilla maculata destroy many 

 of the aphids during the spring and autumn." 



A bibliography of 26 titles is appended. 



The durra asal fly (Aphis sorghi) in Dong'ola Province, Anglo-Egyptian 

 Sudan, H. H. King {[Wellcome Trap. Research Lab.] Ent. Bui. 2 [1914], PP- 

 14). — This is an account of the so-called asal fiy of durra (.Sorghum vulgare), 

 the staple grain crop of the Sudan. In the northern Provinces of Sudan this fly 

 confines its attention to durra and garowi {Andropogon halepensis) grown on or 

 near the river banks but not on crops far distant from the river. 



Controlling mealy bugs by the use of their natural enemies, H. M. Armi- 

 TAGE (.1/0. Dul. Cal. Com. Hort., 8 (1919), No. 5, pp. 257-260).— This is an out- 

 line of the work of the California State Horticultural Commission against the 

 citrus-feeding mealy bugs in southern California. 



A new scale insect (Xylococcus alni) on alder, with special reference to its 

 metamorphosis and anatomy, K. Oguma (Jour. Col. Agr. Hokkaido Imp. Univ., 

 8 (1919), No. S, pp. 77-109, pis. 3, fig. 1). — This is a report of studies extending 

 over a period of several years of a new scale' which infests the branches of 



'In 'O-yO-Konchiugaku, edited by S. Matsumuia (1917, vol. 1, p. 294). 



