ECONOMIC ZOOLOGY — ENTOMOLOGY. 257 



being longest in tlie spring, when it varies from 15 to 22 days. In summer tlie 

 shortest period was G days, varying fi'om 6 to 13 days. In the fall it varies 

 from 9 to 13 days. The average period throughout the season for the 13 indi- 

 viduals of the series of first born is 13.1 days. 



" The length of life, like the period between birth and reproduction, varies 

 greatly. During the spring, when lower temperatures prevail, the viviparous 

 forms will live from 30 to 63 days, while in the summer they live from 16 to ^n 

 days, and in the fall over 30 days. The average length of life throughout tho 

 season for the 13 viviparous individuals of the series of first born is 28.9 days. 



" The sexes make their appearance about the first week in October. ... A 

 viviparous female may produce oviparous and viviparous females and males or 

 she may produce only the sexes. Males- and females reach maturity in from 

 15 to 23 days. The female will not oviposit without having first been fertilized 

 and will live, under these conditions, for about a month, her abdomen becoming 

 greatly distended with eggs. . . . AA'hen ready to oviposit, the females crawl 

 down into the leaf sheath, which is usually separated from the plant stem for 

 a i)art of its length and is somewhat curled, and deposit their eggs in this curled 

 portion. The senior author has counted as many as 200 eggs in such a position." 



A description of rearing methods followed is appended. 



The life history of the alder blight aphis, T. Pergande (U. 8. Dcpt. Agr., 

 Bur. Ent. Bui. 2.'i, tech. ser., pp. 28, figs. i2).— The author's long-continued 

 observations of Pemphigus acerifolU Riley, Inhabiting the soft or silver maple 

 (.leer dasycarpum), and of P. tessellata Fitch, inhabiting the alders, have re- 

 sulted in furnishing conclusive proof that these are "merely forms or series of 

 one and the same species, which should now be known as Prociphilus tcssrUata 

 (Fitch)." 



"P. acerifolii issues during the early or middle part of April, or as soon as 

 the young leaves api)ear, from winter eggs deposited the previous fall in 

 cracks or under loose bark on the trunks of maples, on which return migrants 

 from alders had delivered themselves of the true sexes. These young stem- 

 mothers, after hatching from winter eggs, travel upward onto the branches and 

 settle on the midrib of the underside of the young leaflets. Usually there is 

 but 1, though frequently there may be 2, 3, or more on the same leaf, in conse- 

 quence of which, as well as from the increasing irritation, the leaves thus 

 infested exhibit a more or less marked tendency to fold or almost to ' double 

 up' from the midrib do\^Tiward. 



" Under or within this protection or covering there may be observed numbers 

 of larvae and pupfe of different stages, up to 100 or more, in company with their 

 mother, all of which, from early in June to the end of July, or until the supply 

 of migrants has been exhausted, develop into winged migrants, without, how- 

 ever, leaving any larvae behind to continue the series on the maple. These 

 migrants fly then to the alders, which frequently are rather distant from the 

 maples, and settle at once on the underside of the leaves of these shrubs, where 

 they are soon engaged in deiwsiting their larvae, which surround them in a cir- 

 cle of about 20 to 100. These larvae, after feeding for about an hour or so, 

 move to the twigs, branches, or stems of the shrubs to start a new cycle of life 

 for the species. Here a number of generations is developed, after which, from 

 about the middle of September to the middle of October, numerous return 

 migrants are developed, which fly back to the trunks of the maples to continue 

 the cycle of life prescribed by nature." 



The original host plant of this species is, therefore, the silver maple and not 

 the alder, which is a secondary food plant. The most active among the carnivor- 

 ous enemies are the larvae of the lycaenid butterfly Feniseca tarqtiimus, the 

 larvae of the lace wing fly Chrysopa sicheli, the larvae and imagos of 2 lady 



