EXPERIMENT STATION BULLETINS. 



575- 



cause of all this trouble is ordinarily easy to detect because of the appear- 

 ance of the insects on the branches, where they produce knots. 



Fig. 6. Wooly Aphis of Apple (Schizoneura lanigera): a, galls 

 caused by them on apple root; b, wingless, wax-coated form; 

 c, winged form. 



This insect has long been known in the east as a very destructive and 

 important pest. It now exists in some parts of Michigan, but is not as 

 yet widely spread over the State. Every precaution should be taken to 

 prevent its further distribution, and where already established a strong 

 effort should be made to eradicate it if possible. The same remedies that 

 are recommended for the black peach-aphis will prove effective here. 



SCALE INSECTS OR COCCI DS. 



Few other families of insects present such an array of strange and' 

 varied forms as the family of scale-insects. In, this family of anomalies 

 the females are all blind, wingless, and many of them footless as well, 

 while the adult males are provided with wings, feet, and eyes. 



The family takes its name from the scale or covering with which most 

 of its members are provided. Nearly all are small or minute insects, 

 few exceeding one-eighth of an inch in size, while most of them are smaller 

 still. The scale or covering serves the part of a tent or shield to protect 

 its inmate. Among the different species this shield or scale varies greatly 

 in size, color, and form, and in some cases is wanting altogether, but 

 when present it consists of a thin, papery or waxy shelter raised at the 

 center, something after the manner of a limpet, and concealing its in- 

 mate in the space thus formed. The cast-skins of the insect are usually 

 borne on the top or at the end of the shield. A number of closely allied 1 

 insects, that show close affinity on account of similarity of structure, are' 

 classed among the scale-insects although they are not provided with a 

 separate scale. 



The young of all these scale-insects are small oval lice, which run about 

 freely for a short time. As they are very minute and active, they may 

 easily pass on to the feet of birds and insects and be transported long 

 distances by them, when, if they alight on their appropriate food-plant,-, 

 the young scale-insects may start new colonies. 



