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in the first instar ; those on the spruce had their setae thrust 

 into the bark of the t"\vigs where, later, eggs would be deposited and 

 would hatch out as the second generation. The galls formed by the 

 second generation give rise to the adult, winged lice, which migrate 

 to the Douglas fir to oviposit. The young from these eggs remain 

 on the needles until the next spring, when they become mature. Some 

 of the indixaduals from the eggs then laid remain upon the fir, while 

 others migrate to the Engelmann and blue spruces, where they give 

 rise to the stage which remains over the winter. There is thus a 

 migration each year of the two forms of this species ; the Douglas 

 fir should therefore not be planted near Engelmann or blue spruces. 

 Pemphigus betae, Doane, a native of the Rocky Mountain region, 

 feeds especially on sugar-beets, garden beets and mangel-\Mirzels, also 

 on the roots of Aster, Solidago, Iva xanthifoUa and Chenopoclium. 

 During September and October, about one-half of the individuals 

 accjuire wings, leave their summer hosts and migrate to the cotton- 

 woods. Sexual forms appear early in the autumn, while larvae forming 

 galls on the under side of the cotton leaves have been observed by 

 A. C. Maxson and called Pemphigus balsamiferae. This gall has also 

 been referred to P. populicaulis, Fitch, but the latter seems to be 

 confined to the Middle and Eastern States, while P. betae is strictly a 

 Western species. A Ust of species of Pemphigus with their hosts, is 

 given. Thecabius populiconduplifolius, Cowen, has Populus occidentalis 

 for its winter and early summer host and migrates to a species of 

 Ranunculus in late summer and autumn. Some individuals do not 

 leave the latter host in autumn and may be found on it all the year 

 round. Prociphilus corrugatans occurs upon Crataegus as a winter 

 host ; P. alnifoliae, Williams, is found on Amelanchier alnifolia in 

 winter ; Colopha ulmicola, Fitch, has Ulmus americana as winter host 

 and Eragrostis during summer and autumn ; Tetraneura graminis, 

 Monell, which lives on Ulmus americana in winter, migrates to Lersia 

 oryzoides in summer. Eriosoma (Schizoneura) americanum appears in its 

 sexual form in September round the trunks of American elms ; the eggs 

 laid by the sexual forms hatch in the follo\ving spring, causing the leaf- 

 curl gall. The alternate food-plant of the spring migrants is as yet 

 unknown. E. rileyi differs from other members of the genus o\ving 

 to the fact that there is probably no alternate host. E. crataegi, 

 Oestlund, is a bark-feeder, occurring on roots and branches of Crataegus 

 in Colorado ; the second host is unknown. E. lanigerum inhabits the 

 apple throughout the year ; sexual forms migrate in August and 

 September, but the second host is not definitely known. Anoecia 

 corni is found in the egg stage in winter on the stems of Svida stolonifera. 

 Rhopalosiphum rhois is common on Rhus trilobata as a winter host ; 

 in summer and autumn it is found on wheat, oats, barley and Ebjmus. 

 R. lactucae is found on Sonchus oleraceus in summer ; in September, 

 males and sexuparae migrate to Ribes aureum or R. vulgare, where 

 sexual females are deposited. The summer form of R. hippophaes 

 inhabits species of Persicaria ; in autumn, migration to Elaeagnus, 

 Shepherdia and HijjjJojjJuie, takes place. R. pastinacae, found on 

 Umbelliferae in summer, must be distinguished from R. capreae, also 

 on Umbelhferae ; the former species migrates to Lonicera or Zglosteum, 

 the latter to a species of willow. Hyalopterus arundinis, occurring 

 on plum and prune as over-winter hosts, migrates to Phragmites 



