1 66 AN INTRODUCTION TO ENTOMOLOGY. 



occur in this country, ColopJia and Schizoneura. In ColopJia the hind 

 wings have only one discoidal vein ; in Schizoneura they have two. 



The Cockscomb Elm Gall, ColopJia ulmicola. — Among the gall- 

 making species of this section this is probably the most familiar one. 

 The gall is an excrescence or follicle like a cock's comb, which rises 

 abruptly from the upper surface of the leaves of elm ; it is usually 

 about an inch long and a quarter of an inch high ; it is compressed, 

 and has its sides wrinkled perpendicularly and its summit irregularly 

 gashed and toothed ; it is of a paler green color than the leaf and 

 more or less red on the side exposed to the sun ; it opens on the 

 under side of the leaf by along slit-like orifice ; inside, it is wrinkled 

 perpendicularly into deep plaits. The complete life-history of this 

 species is not known. According to Riley and Monell there is a 

 winter egg, which is usually inclosed in the dry skin of a sexual 

 female. This can be found during winter in the crevices of the bavk 

 of the White Elm. The stem-mother which hatches from this egg 

 forms the gall. She gives birth to numerous offspring; these 

 become winged, and constitute the only generation produced within 

 the gall. These winged, agamic females issue from the slit-like 

 opening of the gall ; and each gives birth in the course of a day or 

 so to upwards of a dozen young. These are born as pseudova. 

 They have well developed mouth-parts ; and it is probable that 

 when fully grown they give birth to the sexual generation. 



To the genus Schizoneura belong several of our most conspicuous 

 'Woolly Aphids." Among them are the following: 



The Alder Blight, SchizoneTira tessclldta. — This woolly louse is 

 often found crowded together on the under side of the branches of 

 alder {AInns rubra), and concealed beneath a covering of downy ex- 

 cretion. It also excretes abundantly honey-dew. 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 secretion. There is also a curious fungus which grows in large 

 spongy masses immediately beneath the cluster of plant-lice ; this is 

 known to botanists as Scorias spongiosum. It is evidently fed by 

 the honey-dew that falls upon it. 



The Beech-tree Blight, Schizoneura imbricator. — This infests both 

 the twigs and leaves of beech. Like the preceding species it oc- 

 curs in clusters of individuals, each of which is clothed with a con- 

 spicuous downy excretion. These clusters often attract attention 

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

 and down, the plume-like masses of excretion rendering them very 



