University of Minnesota Agricultural Experiment Station The Coccinellidae (Ladybird Beetles) of Minnesota (Coleoptera) Wm. C. Stehr Division of Entomology and Economic Zoology UNIVERSITY FARM, ST. PAUL CONTENTS Page Biology and characteristics 5 Summary 13 Key to the Minnesota species of Coccinellidae 13 Literature cited 52 ELYTRA THORAX EYE FRONT- f/61 front view of' F/0/I firont view of/h;opo- Chilocoreis to show front ec7/7ile to show front no/ extendiny before eyes. extern:O./79 before eyes FRONT AP/CAL LATgA)AL "0,41?73 - Of' THORAX BASAL J 71-/- ORA x SCUTEL L UM 8,4.5-AL HUMERAL EL YTRA L 5(in/Re- D/SCAL LATERAL PARTS OF EL YTRA L'ZYTRA AP/CAL F/C ///. Dorsa/ view ofa Coccine///o' 0/;o,00den7/;9) to show ,ocrpts of the thorax and e/yfra. Quadrate J Ociedrete Sii77,o/e tooth tooth inner Outer c/eW A. Claw of 8. C/aw of C. C/akv of C/aw Co CC/>7 e//a • Chi/ocorus /Ve0/77y.rth Fle. /V B/e79/-c7/77.7 of the C/akvs of Coccine///ds. THE COCCINELLIDAE(LADYBIRD BEETLES) OF MINNESOTA WM. C. STEHR BIOLOGY AND CHARACTERISTICS The Coccinellidac, commonly known as ladybird beetles or lady "bugs," have long been of interest because of their habits, both bene- ficial and destructive, and because of their attractive coloration. Many references to them occur in the literature and folklore of medieval times. In Scandinavia the number of spots on the wing covers was believed to indicate whether the prices of grain would be high or low. If there were more than seven spots the price would be low and if less than seven the price would be high. In Germany, France, and England girls would catch beetles and allow them to fly from their hands; the direction they took was believed to indicate the direction from which their lovers would come. There are many references to their beneficial nature, and the esteem in which they were held by earlier generations is still reflected in the common names applied to them in some of the European countries today. In France they are called "les bêtes du bon Dieu" (the creatures of the good God) and "les vaches de la Vierge" (cows of the Virgin) ; and in Germany they are often called "Marienkafer" (Mary's beetles). There are upward of 1,5oo species of Coccinellidae in the world, about 300 in the United States, and of these probably 5o species occur in Minnesota. By far the greater number of species are beneficial to mankind, and, fortunately, all found in Minnesota belong to this group. In general the tribe Epllachninac are plant feeders and thus are eco- nomic pests. Only two species of any importance in the latter group are found in the United States. One of these, the Mexican bean beetle, Epi/achna corrupta, ranks as a major pest in our southern states.. It appeared in the semi-arid region of Arizona, New Mexico, Colorado, and western Texas about 1864 and for many years was confined to that region. Its original home was probably in southern Mexico or in Central America. It attacks leguminous crops, especially beans, and causes great economic loss to the growers by destroying the leaves of the plants. In 1920 it was accidentally introduced into the region near Birmingham, Alabama, and since then has spread very rapidly throughout the southeastern and eastern states. In 1928 it had reached Pennsylvania, New York, Ohio, Indiana, Michigan, Kentucky, Tennessee, Mississippi, and all states nearer to Alabama. There are also several records from the 6 MINNESOTA TECHNICAL BULLETIN 75 Province of Ontario, Canada. Today the majority of the states east of the Mississippi River have to cope with this pest, which very often entirely destroys the bean crop in certain districts. Soybeans are espe- cially injured by it. How far this pest will spread is not known, for each year sees further advances to the north and west. Only Illinois and Wisconsin are between its northern limits and Minnesota today. Dusting or spraying with arsenicals is the most effective control, but the arsenical dust or spray must lodge on the under side of the leaves, for the beetles eat only the under surface and internal tissues of the leaves, leaving the tough upper epidermis untouched. The other species, Epilachna borealis, feeds on cucurbits. It is not, however, the serious pest that the Mexican bean beetle has become. The other Epilachninae are mainly tropical species and the chances of their establishment in Minnesota are small. There are many species in Mexico and South America but most of them feed on native plants, especially of the family Solanaceae. In southern Europe and Asia, Epi- lachna chrysomeliiia is a serious pest, and in Australia Epi/achna 28- punctata causes much damage each year. But the Epilachninae are the aberrant group of the family and the others are, in general, among the best insect friends of the farmer, fruit grower, and nurseryman. The other groups feed mainly on plant lice, scale insects, eggs and larvae of other insects, and on pollen of plants and spores of fungi. S. A. Forbes (1883) examined the stomachs of 39 beetles and found the following percentages of food eaten: 37 animal food (mainly aphids and scale insects) 45 spores of fungi 4 lichens 14 pollen (mainly of grasses and weeds) These are fairly erepresentative of the food of Minnesota species. Wadley (1928), in a study of the ecology of the green bug, Toxop- tera graminum, made sonic observations on the number of aphids de- stroyed by various Minnesota lady beetles. The following are some of his data: Grain Species Stage in life aphids eaten Coccinella 9-notata Larva up to pupation 133 Coccinella 9-notata Adult female per day 85 Coccinella 9-notata Adult male per day 50 Coccinella transversoguttata Larva up to pupation 104 Hippodamia convergens Larva up to pupation 124 Hippodamia convergens Adult female per day 50-75 Hippodamia convergens Adult male per day 30-40 Hippodanfia /3-pit/feta/a Adult beetle per day 30 Hippodamia parenthesis Pair of adults per day ' 46 COCCINELLIDAE OF MINNESOTA 7 Wadley calculated hypothetically that a pair of Coccinella 9-notata Herbst would wipe out a colony of 1,000 grain aphids in less than a week. Cutright (1924) gives similar data for Hippodantia 13-punctata (L) throughout its life. Av. aphids Maximum Mininnun Instar destroyed no. no. First 17 38 7 Second 16 31 5 Third 32 56 io Fourth 55 82 25 Adult female 42 aphids per day. Adult male 20 aphids per day. It is difficult to estimate how much benefit the lady beetles render in the control of plant lice, but it is certain that unless the outbreak gets very severe, they exert a great limiting influence upon their multi- plication. Many cases are on record of outbreaks on apple trees, grains, and vegetables that have been efficiently controlled by some of the common lady beetles. Aphids are the most common food of the Minnesota lady beetles. Some, as Hyperaspis binotata (Say), feed on scale insects. A few years ago the young pines at Lake Vadnais, St. Paul, were badly infested with scale insects. In the summer of 1929 Hy- peraspis binotata (Say), a little black beetle with a red spot on each wing cover, became very numerous and in the unsprayed por- tion of the plantation was very effective in diminishing the number of scales. L. W. Orr reported the same beetle at work on scales in Hubbard County the same year. Since food was plentiful, the beetles multiplied rapidly and by midsummer thousands of larvae were busily devouring scales. The larvae attack the young scales and eggs under the old females. They take a position near the females and then insert their heads under the bodies of the scales and start .fceding on the young and eggs. They bite into the young scale and suck out the body fluids, then puff up the body of the scale several times as if they were blowing up balloons. This is probably a means of loosening the soft internal parts of the scale from the exoskeleton. Finally the body is sucked dry and the hard outer body covering cast away. Larvae ob- served by Mr. Orr and the author ate an average of one young scale each 2/,1 minutes. 'Speaking of the same species, Simanton (1916) says: "One of the most effective enemies of the Lecanium scales is the coccinellid beetle, Hyperaspis binotata (Say). Throughout the spring and early summer the larvae, conspicuous by their flocculent covering, could be found in large numbers feeding upon immature scales and over-turning the adult scales. The adult beetles do not feed upon the mature scales, 8 MINNESOTA TECHNICAL BULLETIN 75 but they destroy the young and also attack aphids and other soft-bodied insects." J. B. Smith (1904)• reports the same species as "reducing an in- festation of Pulvinaria spp. at Montclair, N. J., from 500 to 1,000 scales per leaf to about one dozen scales per leaf." In California the lady beetles have been used more than anywhere else in the control of pests of orchard and field crops. The story of the introduction of foreign species of lady beetles to control the dreaded citrus scale is one of the most interesting chapters in the history of biological control. In 1868 the fluted, or cottony, cushion scale, Icerya purchasi Maskell, was introduced into California at Menlo Park, near San Francisco, on some orange trees from Australia.