422 AN INTRODUCTION TO ENTOMOLOGY 



in the regions where it occurs, as their covering of flocculent excretion 

 renders them very conspicuous. These colonies are of especial in- 

 terest, as within them is found the predacious larva of the wanderer 

 butterfly, Feniseca tarquiniiis, which feeds on the aphids. 



In the late stunmer or early autumn the last generation of wingless 

 agamic females bring forth young, which winter among the fallen 

 leaves at the base of the alder and return to the branches in the 

 spring. From this there appears to be no need of an alternate host. 

 But it was found by Dr. Patch that at the same time that the form 

 that hibernates at the base of the alder is produced, winged migrants 

 appear and fly to maple trees, where they give birth, in the crevices 

 and rough places in the bark, to males and oviparous females. Each 

 of these females produces a single egg. From these eggs there hatch in 

 the spring aphids which pass to the lower side of the leaves of the 

 maple, where they become conspicuous on accotmt of their abundant 

 and long woolly excretion. In this period of its existence this species 

 is the well-known pest of the maple that has long been known as 

 Pemphigus acerjdlii, which name must now be regarded as a synon^mi 

 of Proctphilus tesselldtus, the older name. In July winged migrants 

 are developed on maple which fly to alder. 



The alder-blight excretes honeydew abundantly; the result is 

 that the branches infested by this insect, and those beneath the cluster 

 of aphids, become blackened with fungi that grow upon this excretion. 

 There is also a curious fungus which grows in large spongy masses 

 immediately beneath the cluster of plant-lice; this is known to bot- 

 anists asScorias spongiosa. It is evidently fed by the honeydew that 

 falls upon it. 



The beech-tree blight, Prociphilus imbricdtor . — This infests both 

 twigs and leaves of beech. Lilce the preceding species it occurs in 

 clusters of individuals, each of which is clothed with a conspicuous 

 downy excretion. These clusters often attract attention by the 

 curious habit which the insects have of waving their bodies up and 

 down when disturbed. When an infested limb is jarred, the aphids 

 emit a shower of honeydew. Owing to the abundance of this excretion, 

 the branches and leaves of an infested tree become blackened by 

 growths of fungi, as with the preceding species. The life-cycle of this 

 species has not been determined. 



h. THE GALL-MAKING ERIOSOMATIN^ 



Certain members of this subfamily cause the growth of remarkable 

 galls, resembling in this respect certain members of the following 

 subfamily. Among the gall-making Eriosomatinee that are most likely 

 to attract attention are the following. 



The cockscomb elm-gall colopha, Colopha ulmtcola. — There are 

 two species of aphids that make similar galls on the leaves of elm. 

 These galls are commonly known as cockscomb ekn -galls on account 

 of their shape. Those made by the two species of aphids are so 

 similar that a description of one will apply to the other. In each case 



