Technical Bulletin No. 504 January 1936 UNITED STATES DEPARTMENT OF AGRICULTURE WASHINGTON, D. C. ORIUS INSIDIOSUS (SAY), AN IMPORTANT NATURAL ENEMY OF THE CORN EAR WORM lïy G. W. lîAKiîKit ÁHsooiate eniomologíHt, Division of Cereal and Forage Insect Investigations, Bureau of Entomology and Plant Quarantine CONTENTS Page Page Introduction 1 Food habits of adults.. 12 Economic imi)ortance 2 Length of life of adults.^.. 13 Review of literature 2 Proportion of sexes 13 Onus insidiosas in relation to the corn ear Oviposition __. 14 worm 2 The egg .-, 14 Orius insidiosus in relation to otber insects Places chosen for egg laying __. 14 and to mites '¿ Relation of food of adults to their egg-laying Seasonal history ^_ 4 capacity _ 15 Before corn becomes available 4 Relation of size of eggs to-the egg-laying On the corn plant 4 habits 17 A bundance on corn plants in their several stages Incompleted oviposition __ 18 of growth 6 The nymphs 18 Occurrence on the several parts of the corn Number of generations on corn 18 plant --. _ 8 The importance of Orius insidiosiis in the nat- Relative attractiveness of different varieties of ural control of the corn ear worm 19 corn 10 Summary 21 Relationship of the seasonal history and abund- Literature cited _ 22 ance of Onus insidiosus on corn plants to the cornear worm _ 10 INTRODUCTION In the coiirso of a study at Richmond and CharlottesTÍlle, Va., from 1924 to 1927, on field oviposition by the corn ear -worm {Helio- this obsaleta Fab.) and the fate of the eggs deposited on corn, it was found that the most important natural destroyer of ear worm eggs, especially those deposited on corn silks, was the small antho- corid bug, Ornis ¡n.sidiosus (Say), formerly known as Triphleps in- sidiosus'. The writer has previously observed its abundance on corn and its important relationship to the European corn borer in Mas- sachusetts (^),^ and the literature showed that it was widely dis- tributed, not only on corn but on many other plants, where it fed on numerous small insects many of which were injurious to crops. All of this information was fragmentary, and it appeared that little ^ Italic numbers in parentheses refer to Literature Cited, p. 22. 20240°—;í6 1 4 ¿ TECHNICAL BULLETIN 5 0 4, U. S. DEPT. OF AGEICULTUEE was known about the biology or economic importance of'this useful predator. During the years 1928 and 1929, in the vicinity of Rich- mond, Va., the writer learned much more about this species, especially as found on the corn plant and as related to the corn ear worm, and the information gained in this study is summarized in the present bulletin. ECONOMIC IMPORTANCE Orius insidiosus apparently occur.? over most of the United States and in southern Canada. Records in literature show its occurrence in 31 States a.s well as in 2 Canadian Provinces. It occupies among the Heiniptera a position similar to that occupied by THchogramnna iThinutmih Eiley among the parasitic Hymenoptera, for frequently these two small species, taken together, form the most important natural control of an injurious insect, especially among those attack- ing the corn plant, the one destroying the eggs alone, and the other feeding on both eggs and newly hatched larvae. M. V. Jones, in an unpublished manuscript, reports that (Triph- lep») Orius insidiosus was found feeding on probably 4 percent of the pupae of the Mexican bean bean beetle {Epilac-hna con'-wpta Muls.) latt> in June 1924. The insects attacked by O. insidiosus, according to the writer's observation in various localities, were among the most important enemies of the com plant in these several areas and included not onlj' the corn ear worm but the European corn borer (Pyrausta niwbiJalis Hbn.). in Massachusetts in 1923 and 1924, the fall army worm {Laphygma frugiperda S. and A.), in Georgia in 1930, and the larger corn stalk borer {Diatraea cramhidoides Grote), in Virginia in 191^8 and 1929. REVIEW OF LITERATURE Notes from published writings show that 0. insidiosus not only occurs widely over the country but is found on a wide variety of vegetation, including trees, shrubs, field crops, vegetables, and many wild plants. On many of these it is found principally on the blos- soms, but it also searches for food over the entire plant. When com is available it lays its eggs principally in the strands' of fresh silk, where also the young nymjihs begin feeding. ORIUS INSIDIOSUS IN RELATION TO THE CORN EAR WORM Forbes records O. insidiosus as an enemy of corn ear worm eggs and {13) notes its abundance on corn. Garman and Jewett {16) reared O. insidiosus from the egg, and figured the eggs for the first time; they reckoned its life cycle from egg to adult as 15 days, 3.25 hours. They state {16, p. 687) : " It appears to feed to some extent on plant juices, but is fond of the juices of various insects, such as species of ' thrips,' and is very useful because of its destruction of the eggs of the corn worm." Mally {¡i¿9, p. 39) noted that this insect was beneficial m destroying bollworm eggs. Quaintance and Brues {36, p. 107), in an elaborate report on the bollworm say: The nymphs and adults of TriphlepK insidiosus Say * * * have been repeatedly observed feeding on bollworm eggs and on very small larvae This little lieteroi)teron is especially abundant in fresh corn silk and is often seen frequenting cotton i)lants also. Although in a number of instances noticed in ORIUS INSIDIOSUS, ENEMY OF CORN EAR WORM 3 the laboratory they suom loath to attack living larvae, they are sometimes to be seen in the field with newly hatched larvae impaled on their slender beaks. Their principal value lies, however, in the large number of eggs which they destroy. A special count was made at Sulphur Springs, Tex., on August lö. 1904, to determine tlie probable proportion of eggs destroyed by this agency. The eggs ou 10 different silking ears were examined, and, on an average, 55 percent of the eggs were found to be shiiveled. It is probable that most oE these sln-iveled eggs had been punctured and their contents sucked out by the Triphleps, which were numerous on the silks at that time. This is no doubt an exceptional case but it serves to show of what great value the Triphleps may be under favorable conditions. Webster {^3) noted as early as 1885 that 0. insidiosus may fre- quently bo found in all stages literally swarming among the corn silks with no other visible food supply. Winburn and Painter {50) state, regarding the corn ear worm : "Among the predators, Onua insidiosii.^ is probably the most beneficial." ORIUS INSIDIOSUS IN RELATION TO OTHER INSECTS AND TO MITES Besides the eggs and j'oung larvae of Lepidoptora, the insects recorded as prey of Orhm insidioffos include thrips, aphids, white flies, leaf hoppers, the young of lace bugs, the chinch bug, midges, red spiders, and mites. One writer (,^<*?) records it as even attacking man. Another {ßO) thought that it transmitted corn-ear rot (Diplo- dia .sp., Fxmarmnh. sp.). Still another (ßff) referred to the feeding and egg-laying injury to chrysanthemums attributed to O. insidiostfíi. A list of insects preyed upon by 0. insidiosus and references to records of such attack in literature follow : Thysanoptera (/-';, p. J/SJ,; J,2) : Thrips tataci Lind. {Ji, 5). Enflirips nirotinnne Hinds (—FranklinicUa fusca Hinds) (18). Eiithrips pyri Daniel (=TneiiiotIiripii itironseqitrns Uzel) {IS). (Eutltri/ifi) ScirtDlhiips citri Moult. (/•''). Fraiilclinieila triiioi Fitch (J!)). Pros'opi>tlirips oognatus Hood (.Í2). Hcliolhrips fasoiatus Perg. (-}0). Homoptera : ' {ñtarraxiphum) Illinoia pisi Kalt. (C; //, p. 151). Phylloxera rififoliac Fitch (12, p. 86; U,; 23). Viizvs hragiiii Gillette (21). Phorodon hiiiinili Schrank (3S). (CJiaitophorus) Pcri¡)liyUiís ncgundinis Thos. (.}.')). (Aleyrode.i) Trialctirodes vaporarioruin We>tw. (16). EmpodSca mail Le Baron (=Emp()a.wa fahar Harr.) (1 ; /i7; JiH, p.//(lO). Hcmiptera : Cnriitlmcha ciliata Say (31, .'/I). Gnrpiipliia solanl Heid. (9). nii.^HUH Icucopferus Say (10; 12, p. H6; IJ,; 2S; .M; U; J,.-,; J,ñ). Lepidoptera : Laphyffma fruffiperda, S. & A. (2Ii). Rhodopliora florida Guen. (7). Piirdusta nuhilalis Hbn. (2). {Phlhorimnea) Onoriino.<«'hemn opcroulrlUi Zeil. (17). Díptera: Dnsyneura leffiiiiiiiiicola Lintn. (//, p. I2S). Acariña (.(7) : Tctramjvlius tcluriu.i I,, (bimafíulatiis Harvey) (8, 2J, 26, 27). In Virginia the writer has found it preying upon several aphids, including 2'ritogeruiphis sp.^ feeding on wild lettuce {Lactuca cana- densis) and Illinoia pisi Kalt.- feeding on crimson clover. ^ Determinad by I'. W. Mason, Bnrcau ol" Kntomoloff.v and Plant Quarantine. 4 TECHNICAL BULLETIN 5 0 4, U. S. DEPT. OF AGBICTJLTUEE SEASONAL HISTORY BEFORE CORN BECOMES AVAILABLE Oriits insidiosi(,s evidently passes the winter as an adult in pro- tected places. Blackman and Stage {3, p. 201) recovered it from dead hickory on the ground. Hyslop {20) states that it is known to hibernate in the rubbish in cornfields. McGregor ajid McDonough (27) say, " These bugs pass the winter in the adult stage and usually become active some time in April, although they have been seen as early as the middle of March." Garman and Jewett (16) say, " It hibernates as an adult among rubbish at the bases of plants." Mar- shall {30) states that the insects hibernate as adults in " any place where the drainage is good and where a fairly good covering of leaves and rubbish can be found." In New England, Parahley (5^) obtained records of adults throughout the season, from June 22 to October 3. In Virginia the writer has seen adults from March to November; but of the large populations that occur in corn during July, August, and September apparently few survive to enter hibernation, and previous to the ap- pearance of com in the field they are rarely met with.