148 ECONOMIC ENTOMOLOGY 



2. Root form similar to that on leaf; often derived from leaf form ; 

 several generations in a season; yellowish and wingless, and forms 

 nodules which break down and decay, often destroying the root. 

 Yellowish oval eggs are laid on the roots. Larvae moult three times. 

 Leaf-galls are most common on American grapes while root-galls are 

 most common on European grapes. 



3. Some of the root forms in late summer develop elongate long- 

 legged winged females that fly to neighboring vines and lay 2-4 eggs 

 beneath loose bark. 



4. These eggs are of two sizes — the smaller producing males, the 

 larger sexual females. These are wingless and minute. Each female 

 lays one large egg from which hatch the following spring the leaf and 

 root forms. Not destructive on sandy soils. 



Control. — Spray in early spring with lime sulphur; use American 

 varieties as stock. 



COMMON GARDEN APHIDS 



Cabbage or Turnip Plant-louse {Aphis brasskce'L.). — Often abun- 

 dant on the under surface of leaves of cabbages and turnips, and very 

 destructive in warm dry weather. A greenish, soft, pear-shaped insect 

 covered with a whitish bloom. Mature forms have black head and 

 eyes and dark cornicles; nymphs are pale green with black legs and 

 antennae. Parasite, Aphidius rapa, a braconid. 



Aphis pseudobrassicae Davis. — Also occurs on turnip, radish, cab- 

 bage, rape, mustard, etc., and is often mistaken for A. brassicce. 



Melon Plant-louse (Aphis gossypH Glov.). — Occurs on the under 

 surfaces of the leaves of melon, cucumber, squash etc., and also on other 

 crops and weeds. Winter eggs have been found on purslane and straw- 

 berry. A blackish-green insect. Apterous females with legs and 

 antennae whitish, cornicles black and short; winged forms with a row of 

 black spots on sides of abdomen, and spots on head and thorax. 



Bean Aphis [Aphis rumicis L.). — Occurs on the tips of horse and 

 broad beans at time of flowering. When the lice are abundant the 

 plants assume a sooty sticky appearance. Also on apple, dahlia, dock, 

 shepherd's purse, pigweed, snowball and burning bush. This aphis is 

 slaty blue or black, with white bands on the legs and often with waxy 

 tufts. Called also the "black fly," "colHer" and "black dolphin." 



Strawberry Root Louse {Aphis forbesi Weed). — Bluish-green, on 

 roots of strawberry; occurs also on leaves. Eggs laid on stems and 



