134 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
tension of the western area to Colorado. Neither species is of great 
economic importance. 
Hormaphis hamamelidis forms conical galls on the upper surface of 
witch-hazel leaves in spring. Hamamelistes spinosus produces galls 
on stem buds of witch- hazel by the feeding of stem mothers in the 
spring. 
Famiry CHERMIDAE 
The genera included in this family differ in their biology from the 
more typical aphids in that both the sexually perfect and i imperfect 
females lay eggs. The sexually perfect forms, both male and female 
and with and without wings, are dwarfed. There are also certain 
differences in the venation of the wings of the imperfect forms that 
set them apart from the usual aphid types. Two subfamilies are in- 
cluded in the family. 
SUBFAMILY CHERMINAE 
The species in the subfamily Cherminae, known as spruce gall 
aphids, are all found on conifers, the primary host being spruce, where 
the entire life cycle is known. The secondary host may be spruce, 
Jarch, pine, or fir. 
Comstock (103, p. 429) stated that the life cycle is complex and 
frequently includes Tn developing of two parallel series of forms. In 
one series the life cycle is completed on spruce in a single year, but in 
the other series it requires 2 years and is passed partly on spruce and 
partly on pine, larch, or fir. The number of generations needed to 
complete the cycle may vary considerably, and there may be a series of 
generations of one form. As many as seven parallel series of forms 
have been found to exist in one species. As with many other gall- 
forming insects, the galls are typical and the species concerned may be 
recognized by them. Annand (3) has brought together information 
on the life history and habits of many for est- inhabiting species. 
The eastern spruce gall aphid (Chermes abietis L. i a species in- 
troduced into this country from Europe early in the nineteenth 
century, feeds principally on Norway and white spruces, although it 
has been recorded from other conifers (Friend, /67, 169; Patch, 335, 
336). 
Stem mothers of Chermes abietis deposit their eggs at the bases of 
buds in May. Nymphs hatch in about a week, crawl to the needles 
at the base of the new shoots, and settle on those that have become 
swollen by the feeding of the stem mother. These needles continue 
to swell until a gall is “formed (fig. 28, A), each pocket of which may 
cover a dozen nymphs. Late in the summer the galls open and allow 
winged female adults to emerge. These, in turn, deposit their eggs 
on the needles of the host (fig. 28, 8) and die immediately thereafter. 
Their dead bodies remain as coverings for the egg masses. The eggs 
hatch in 2 weeks and the nymphs crawl to the current year’s growth, 
where they begin to feed. Only the nymphs that have fixed themselves 
to the bases of buds survive the winter. The overwintering nymphs 
mature in April and May, giving rise to the stem mothers, which are 
covered with white, waxy threads (fig. 28, (’). 
Injury to the host tree is caused by the formation of pineapple- 
shaped galls at the bases of the twigs. Not all the twigs so infested 
