INSECT PARASITES AXD PREDATORS OF INSECT PESTS 3 



sites for liberation on every farm or orchard, but the colonies are 

 placed at such intervals that natural spread will soon provide a 

 thorough distribution. 



The foregoing statements apply entirely to the use of imported 

 parasites. Various attempts have also been made, however, to extend 

 the usefulness of the parasites native to this country. In some in- 

 stances this has been done with marked success, but these instances 

 have represented transfers of parasites from one part of the country 

 to another to which their natural spread has been prevented by vari- 

 ous physical barriers. In general, it may be stated that there is 

 little possibility of securing increased effectiveness by the liberation 

 of additional numbers of a parasite already present in a locality. 



The natural enemies of various crop pests are often inconspicuous, 

 and their presence is not detected by persons unfamiliar with them. 

 Many inquiries are received from growers regarding outbreaks of 

 field or orchard pests in which it is stated that the parasites are 

 absent and that colonies are desired for liberation. To determine 

 definitely the presence or absence of these parasites, the assistance of 

 an expert from the State experiment station or from the Bureau of 

 Entomology and Plant Quarantine may be required. Usually it will 

 be found that the parasites are already present, though possibly only 

 in small numbers. Local or temporary conditions may be unfavor- 

 able to them and, if so, the same handicaps will restrict the increase 

 of any colonies that might be liberated. The Bureau of Entomology 

 and Plant Quarantine does not maintain stocks of either native or 

 imported parasites for general distribution to growers. The im- 

 ported ones are colonized directly and in accordance with a definite 

 plan of distribution. 



ENEMIES OF APHIDS, SCALE INSECTS, AND MEALYBUGS 

 LADYBIRD BEETLES 



The beetles of the family Coccinellidae, known variously as " lady- 

 bugs ", " ladybirds ", " ladybird beetles ", or " lady beetles ", are 

 among the most common of all beneficial insects. Various species 

 of these useful insects are widely distributed and often occur in 

 enormous numbers. These beetles and their larvae feed upon a wide 

 variety of insects, though more particularly upon aphids. scale 

 insects, mealybugs, white flies, and red spiders. The various species 

 do not feed indiscriminately, however, but each is more or less 

 restricted to a particular insect or group of insects. Aphid-feeding 

 species, for instance, do not generally attack scale insects, nor will 

 feeders on mealybugs normally attack either scale insects or aphids. 

 Several species are known to feed exclusively upon fungi, but these 

 species are seldom encountered. 



In this family there is one group, represented in this country by 

 the genus Epilachna, which feeds exclusively on plant foliage and is 

 consequently harmful. The best known example is the Mexican 

 bean beetle (Epilachna corrupia Muls.), which was introduced into 

 the Eastern States from the Southwest about 1920, has spread north- 

 ward in recent years, and is now very injurious to the bean crop in 

 most of the States east of the Mississippi River. The adult beetle's 

 of this species may be recognized by the form of the body, which is 



