Proceedmqs of the 7th Iniernatumal Workmg Conference an Stored-product Protectwn - Volume 1

The white-marked spider , fur (L.) in stored grain - biology, seasonal occurrence and control using a surface insecticidal admixture

DM Armitage", M P Kellyl, K Amos' , S Schaannmg/ and W Spagnolr'

Abstract conditions, relatively poor hygiene, and the presence of

Ptuius fur (L ) has recently been identified as the most vertebrate pests inside the building Some of these species frequently occurnng, If not the most numerous, beetle pest are quite slow breeding, usually With only one generation of Bntrsh gram stores Previous work has mdicated that It IS per year One such IS the white-marked , a nocturnal species and free-roaming adults occur between Pimus fur (L) which has hitherto been mostly October and June It pupates m August and eggs laid after disregarded and no Significant research has been conducted the turn of the year diapause as larvae until the following on ItS control III bulk gram year Females need free water to OVIPOSItand estimates of In a recent survey of commercial gram stores (Pnckett total eggs laid range from 38 - 100 while longevity estimates and Muggleton, 1991), ptmids were second only to mites vary between 84 and 224 days Records of pitfall trapping m and psocids m frequency of occurrence of mvertebrate pests two British stores showed that senous infestations developed (Table 1) Pimus fur was the commonest ptimd and was on gram stored for 4 years or more, With seasonal outbreaks found on 37% of 157 sites or 25% of 283 stores It was also in winter Adults of two populations from different stores present m 22% of 187 mills (Prickett, 1994) The mere were exposed to pmmiphos-methyl and etnmfos for 2 and 7 presence of an msect does not necessanly indicate a senous days and the latter pestrcide produced a higher mortality As infestauon but nevertheless IS enough for a market rejection a result of these pronusmg laboratory efficacy tests, a full of the gram However, senous infestations do occur and 4 scale surface treatment was earned out III a 16,000 tonne III bulk gram store The surface treatment was very uneven stores on 2 sites the Midlands have suffered ptmid and exceeded the recommended dose but It was clear that It problems smce November 1988 largely eradicated the mfestation, despite the natural decline m spider beetle population throughout the test There was Table 1. The number and proportion of commercial sites and no apparent difference between the effectiveness of the 2 stores thereupon m which Ptmus was detected pesncrdes m this commercial-scale test Sites Stores No % No %

P fur only 45 28 7 57 20 1 P fur + P tectus 31 8 3 13 46 Introduction P fur + P pusdlu« 1 o 61o 4 Bulk cereal grams stored for extended penods m the UK are Total 59 37 0 71 25 1 always at nsk from mfestation by a range of msect and mite storage pests Many of these are well recognised, and their It IS clear that this IS one species whose pest status IS prevention and control has been the subject of research for many years In addition to these "pnmary pests', It has changing or has already changed and accordingly, a long been known that gram stores frequently carry a lower prehmmary research programme was mrtiated This level of infestation of 'secondary pests' , many of which are compnsed a summary of known aspects of the msect's associated With long storage penods, undisturbed biology, a collection of records of population changes in a commercial store, hrruted laboratory trials on the efficacy of etnmfos and pmmiphos-methyl on adults and an attempt to 1 Central Science Laboratory. Muustry of Agriculture, Fisheries and Food. Sand Hutton, York Y04 ILZ UK elmunate the pest on a commercial scale by a surface

2 Grovemere Merchants. Lancaster Way, Ely. Cambndgeshire CB6 admixture expenment which incorporated a companson of 3NP both chemicals 51 Proceedmqs of the 7th Internatwnal Workmg Conference on Stored-product Protection - Volume 1

as low as 8°C (Godan, 1952) A small proportion of adult A Brief Summary of the Biology males has been observed to fly (Woodroffe, 1953) and of maximum activity occurs at 10-1St: The biology was systematically studied by Howe and The natural history of this species was studied by Braune Burges (1951) from whom Table 2 has been extracted (1948) and most of the details that follow relate to his They used vanous diets to raise the msects but as the study Eggs are laid m sheltered places where they adhere differences between most of them were not significant, the and develop mto active larvae which normally develop figures below are based on average values for the 3 diets No through 3 mstars They pupate m August m a cavity which diapause was noted at 30t: but eggs did not hatch Mortality they seal With webbmg, where they develop mto adults of larvae vaned from over 50% on wheatfeed at 30t: and at which remam for a penod m the coccoon while they mature 20°C, about 23% on fishmeal at 23t: to 7- 8% on sieved sexually The adults are only found between October and fishmeal and a synthetic diet at 23°C June and die off m the latter month Larvae from eggs laid Braune (1948) gave figures of 26 days for egg between October and December enter the pupal stage the development under ambient conditions, 18 - 19 days for followmg summer Those laid between March and June are pupal development and 30 - 35 days for the penod m the not fully grown by August and walt a further year before cocoon Pre-oviposition was up to 20 days but more normally pupal metamorphosis takes place There are only 2 mstars m 10 days when sufficient fluid was available Five eggs laid m this case, so the full penod of development IS well over a late October, early November took 10 - 11 months (300- year The turn of the year marks the boundary between 360 days) to become adults Two laid m late Apnl , early these two types and about 1/3 of the eggs laid then complete May took 17 and 19 months (510 - 570 days) while 2 laid m development m the same year and the remamder contmue January took 9 months (270 days) and 21 months (630 mto the second year This' diapause ' makes the production days) of large numbers for laboratory studies problematical and Howe and Burges (1951) found that only 38 eggs were this explams the dearth of information on an Important and laid by females, mamly over a 12 week penod but Braune Widespread pest Howe and Burges (1951) noted that all (1948) quoted 100 as the figure m the summary of his study their diapausmg msects were males and obtamed as many as 168 (52, 44, 168, 56) usmg a diet The adults are scavangers and, as well as foodstuffs Will of dead flies and milk This extended the life to about 9 eat dead , for mstance m the nests of wasps, rodent months or 148 days (88, 162, 149, 90, 173, 224 days) faeces, skms of birds and mammals and are a pest of compared to 32 - 59 days when starved or on a diet of rye museum specimens However, for maximum productivity, bran and flies Howe and Burges (1951) stated that males they benefit from a protemaceous diet and free water IS Irved , on average for 12 1 weeks (85 days), females for 14 essential for the female to produce eggs weeks (98 days) Zakladnoi and Ratnova (1987) also give They aVOId light and are mamly nocturnal, activity figures of longevity of adult P fur at moderate (Table 3) peakmg between 10 p m and 11 p m Most are found m and survival times at low (Table 4) temperature November Oviposition has been observed at temperatures

Table 2. Time m days for the development of Ptvnus fur at 70% r h (abridged from Howe and Burges, 1951) Temp °C 30 23 20 no diapause diapause no diapause diapause egg penod x 16 5 19 5 larva 88 5 64 4 288 5 68 5 352 6 pupa 17 8 16 6 17 7 18 8 21 1 pre-emerg 39 41 2 44 2 53 6 38 4 egg-adult 96 8 329 2 106 7 368 3 egg-emerg 136 4 370 7 158 6 411 3 x = no development -=no data

Table 3. Longevity of P fur (days) accordmg to L Gurvich [CIted m Zakladnoi and Ratnova (1987) ] °C 10-13 15 -18 18-22 23-15 25-30 males 42-59 32-61 46-61 24-49 11-18 females 38-92 62-71 61-113 34-87 10-30

52 Proceedings of the 7th International Working Conference on Stored-product Protection - Volume 1

Table 4. Low temperature longevity of P. fur stages (days) incubation, during initial visits to the 2 bulk grain stores. at 75% r. h. after R. Ushatinskaya [cited in The emergence of from these samples was very Zakladnoi and Ratnova (1987) J. slow, producing only low numbers of adults and as a result, larger numbers of adult beetles were collected directly from 'C 0 -5 -10 -15 the store to be used in preliminary tests. Two admixture adult 79 72 29 9 pesticides, pirimiphos-methyl (Actellic) and etrimfos egg 186 97 31 9 ( Satisfar ), commercially available as 0.2 % active larva 219 164 36 17 ingredient dust formulations, were used in these standard laboratory toxicological tests. These dusts are the only pupa 49 40 13 6 formulation approved for admixture to the surface of a bulk of grain. Other contact pesticides approved for admixture Population Changes in are available only as liquid formulations, and are intended Bulk Grain Stores for admixture to grain during filling of the shed or turning of the grain. The tests were set up to assess the efficacy of the Long-term records of numbers of P. fur caught in pitfall two dust formulation insecticides approved for admixture to traps were obtained from 2 bulk grain stores cooled with the surface of bulk grain, against spider beetles. The ambient air and holding grain from the 1984 harvest. The insecticides were admixed to grain and insects exposed to surface of each store was divided up into quadrants and the the grain for two and seven days. traps in each quadrant were assessed in succesive weeks . The results show the average per trap caught in all 4 quadrants over 4 weeks, i. e. average numbers per month per trap. The first store contained about 9,500 t of barley. There were 9 traps in each quadrant, thus the average was based on 36 traps per month. The observations cover 32 months. The second store held about 16,000 tonnes which was loaded at the end of 1985. The surface measured about 57 x 60 m and the grain depth was about 7m. There were 20 traps in each quadrant. and the observation period covered 55 months. Trapping records were not obtained between February and April 1991. Records of temperatures in the grain bulk (usually 6 - Fig. 1. Changes in the number of P. fur in 36 pitfall traps 12'C ) and moisture contents of the grain, (usually about 13 with time over a 32 month pericxl in a 9500 t bul' - 15 % ), were available but are not presented here, since barley store. the largely surface-dwelling Ptinus would be experiencing the rapidly fluctuating ambient conditions. Fig. 1 shows 50 three successively-increasing peaks in the winters of '89 - 45 90. '90 - 91 and '91 - 92, with a second peak in Spring '90 40 35 and Spring '92 which was absent in Spring '91. No insects 30 were found between June and October '90 (4m) and from 25 February to September '9l(8m). Fig. 2, likewise shows the successively-increasing peaks in the winters of '88 - 89, '89 - 90 and '91 - 92. The :: t incomplete records for winter '90 - 91 explain the interrupted population. Peaks are also evident in May '89 ': L++-+-H"'M"H-i''f''t-t+-H¥ and May '91. The highest numbers per trap averaged nearly 50 in Jan. '92, immediately before an experimental surface P. treatment in Feb. '92, after which numbers fell to one- Fig. 2. Changes in the number of fur in 80 pitfall traps tenth. with time over a 55 month period in a 16,000t bulk barley store. Preminary Laboratory Method Admixture Tests o .lg of pirimiphos-methyl dust was weighed out and added Grain samples were brought back to the laboratory for to 500g of grain in a glass jar. This gave an intended dose of 53 Proceedmqs of the 7th Iniernaiumal Workmg Conference ml Stored-product Protecium - Volume 1

4mglkg of active mgredient The Jar was tumbled for fifteen some control mortaltty was mevitable mmutes Immediately after the addition of the msecticide , After 48 hours exposure, the contents of the Jars were left overmght and then tumbled agam for a further fifteen assessed one at a time and any msect mortality recorded mmutes on the followmg day Tlus method was repeated for The gram and msects were then carefully returned to their the etnmfos dust appropnate Jar and returned to the controlled conditions Approximately 50g of gram was then placed mto 100ml After a further five days exposure, the contents of the Jars glass bioassay Jars, three repltcate Jars bemg set up per were re-assessed and any further mortaltty recorded insecticidal treatment An additional three Jars were set up Results WIth untreated gram to act as controls All of the Jars of gram were then left at constant conditions of 25'C and 70% Both populations of spider beetles showed a high mortality rh overmght to equihbrate agamst both pesticides after 2 days With Etnmfos apparently Twenty-five healthy lookmg spider beetle adults, which producmg the better results (Table 6) The effect of the had been previously collected from the 2 held trial sites, pesticides after 7 days was not clear however, because of the were then added to each of the Jars The Jars were then high control mortaltty This was likely to be due to the fact sealed and returned to the above conditions It was not that these beetles prefer a lower temperature and higher possible to use msects of a known age for these tests and as humidity than that provided by the standard bioassay test the adult life of spider beetles is so short, together With the The results were deemed of sufficient promise to Justify a fact that they prefer a substrate of higher moisture content, full-scale surface treatment man mfested commercial store

Table 5. The mortality (%) of Pimus fur (n = 25) at 70% r h , 25'C exposed on gram to 4 mg/kg pmrmphos-methyl and etnmfos dust formulations for 2 days

Store 1 Store 2 Control P-m Etnmfos Control P-m Etnmfos

mean 12 36 66 15 46 79 max 19 48 72 29 60 80 lllln 4 16 58 43276

Table 6. Companson of pesticide residues (rng/kg ) at the surface of a gram store m an untreated area ( n = 5), 2 areas treated WIth pmrmphos-methyl (n = 2;< 7) and 2 areas treated WIth etnmfos (n = 2x7)

Month February March May June Week 4816 20

Untreated (P-m) mean 1 30 119 129 o 8 max 3 20 22 32 34 mm < 01 o 38 o 14 o 08 Untreated (Etnmfos) mean o 024 o 08 < 01 < 01 max o 12 o 12 < 01 < 01 mm < 005 o 05 < 01 < 01 P-m 1 mean 9 0 929 12 96 5 2 max 14 7 19 32 11 lllln 2 61 37 32 14 P-m2 mean 139 118 17 3 135 max 28 3 22 68 27 mm 7 18 73 37 38 Etnmfos 1 mean 16 6 14 46 10 47 8 7 max 57 0 31 25 20 lllln 159 33 o 76 o 35 Etnmfos 2 mean 9 6 15 69 14 33 19 9 max 23 9 41 31 64 mm 270 19 17 79 54 Proceedmqe of the 7th Inierruuumal WOl'kmg Conference on Stored-product Protectwn - Volume 1

Smce the pesticides to be used were dusts, the control Surface Admixture of Etrimfos area was masked With polythene sheetmg throughout the and Pirimiphos- Methyl in a application to prevent, as far as possible, the surface of the ~ulk <;rain Store gram m tlus area becommg contammated With dnftmg dust The treatments were carried out over two days, two A large store contammg around 16,000 tonnes of barley quadrants bemg treated Withetnmfos on day 1 and the other from the 1984 harvest was used for this field trial The bulk two quadrants being treated With pmrruphos-methyl on day of gram was stored m an essentially rectangular formation, 2 By allowing a pause overnight between treatments With with a large, well raked and flattened area extendmg from the different pesticides, and by masking the quadrants that one end of the shed for approximately 57 metres, 60 metres were not bemg treated on the day With polythene sheetmg, Wideand 7 metres deep This bulk sloped down at the other It was mtended to muunuse contarmnation by dnftmg dust end, the slope being approximately 16 metres m length and On day 1, each quadrant to be treated With etnmfos was with a nearly constant Width Duckboards were arranged divided mto 2 metre bands and the etnmfos was applied at a across the gram surface permittmg easy access from the rate of 50g/m2 (to give an intended recommended dose of sides of the gram wallmg 4mglkg), by carefully sprmklmg, from bags, pre-weighed Initial inspections revealed that the spider beetles were amounts of dust over the surface of the 2 metre bands of predommantly surface-dwelling, With almost no msects gram The dust was then raked into the surface of the gram bemg found at a depth greater than 2 or 3 centimetres to an approximate depth of 30cm, using a long-tmed wooden The surface area of the gram bulk, measunng rake On day 2, the other two quadrants were treated With approximately 4380 m2, was marked into sectors, and an pmrruphos-methyl by the same method and at the same extensive number of pitfall, PC and probe traps, mcludmg application rate, to give the same mtended recommended those used by the store management, were momtored at dose frequent intervals to establish the level of spider beetle Treatment of the level area of the bulk was relatively population It was known from an examination of the store- simple, but treatment of the surface of the gram slope was keeper's records over the previous two years, that adult more difficult as the dust had to be broadcast down the slope beetles appeared m significant numbers dunng January from a distance With the possibility of achievmg a slightly through to March Another emergence, though usually of less even treatment than was obtamed on the level areas smaller numbers, also occurred dunng May (Figs 1 and Nearly 100 kg each of the 2 pesticides were used, costmg 2) It was hoped that a practical field trial could be £ 363 (18 2p/m2) for the pmrmphos-methyl and £ 251 undertaken dunng the first adult peak, and momtored (12 6p/m2) for the etnmfos at 1992 pnces through the expected second peak of activity m) Post-treatment trapping PC traps (Cogan et al , 1992) were placed on the gram surface of the control area, Layout of the field trial at approximately 5 metre mtervals, pnor to treatment and I) Pesticides Smce the spider beetles were restricted to sheetmg, and followmg treatment on the treated areas The the surface of the gram, a surface dust treatment was areas treated With pmnuphos methyl each had 30 traps and considered the most suitable and cost-effective for this trial those treated With etnmfos had 28 There were 39 traps in By mcorporatmg both pmnuphos-rnethyl and etnmfos mto the control area Thus a total of 155 traps were used and the trial, a companson could be made between the these were checked at four-weekly intervals up to twenty effectiveness of the two pesticides under 'field' conditions weeks after treatment, to momtor the spider beetle 11) Treatment logistics The surface of the gram was population divided mto treatment quadrants, leaving a central cross- IV) Chemical analysis Seven samples from both treated shaped band as a control area delmeated by canes and areas and 4 from the control gram were taken for chemical coloured tape Two quadrants diagonally opposite each other analysis on the day of treatment and then at 4, 12 and 20 were treated With pmrmphos-methyl and the other two With weeks after treatment Samples contammg approximately etnmfos The areas treated with pmmiphos methyl 500g were taken With a scoop from the top few centimetres measured 33 9 < 252m and 31 3 /, 341m, those treated of gram Analyses were done to indicate the mimi dosage on With etnmfos were 341m -: 252m and 33 9 x 313m and the gram, ItS persistance on the gram, and to reveal the the two control stnps, formmg the cross, measured 4 4/, extent of any contammation of the control area from 59 6m and 3 1 x 72 4m This pattern was adopted to take pesticide drift clearly noticeable as air-borne dust dunng the account of possible regional fluctuations m mfestatIon across treatments the gram bulk, and also to ensure that the gram slope at the Results one end of the bulk mcorporated a treatment of each of the pesticides The average residues obtamed from surface samples were 55 Proceedmq« of the 7th Iniernaiumal Workmg Conference on Storei-prcduc; Protecium - VOI1WW 1

2 - 5 times the calculated dose (Table 7) With much areas was declmmg but the effect of the insecticide vanation between samples in any given sector, mdicatmg treatment can be seen by companng numbers m the uneven treatment It IS likely that the dose of dust, untreated area With those m the treated areas (Table 8) calculated for a 30cm depth, had not been effectively For instance, 4 weeks after treatment there were at least distributed vertically by the rakmg There was also much 26x as many beetles m the untreated as the treated vanation between samplmgs which means that no quadrants The numbers of msects m the treated and conclusions can be drawn about residue decay About one- untreated areas were sigruficantly different (sign test p < third the recomended dose of pmrmphos-methyl had found o 05) but there were no large differences between msect ItS way onto the control gram, presumably through drift and numbers trapped m the quadrants treated With different tramphng, but much less etnmfos was present This may be pesticides The declme m population m the control area was explamed by the fmer particle Size of the pmrmphos-rnethyl presumably due to the natural seasonal changes, the small formulation clearly noticeable as air-borne dust dunng the chemical residues as a result of •drift' and the effect of treatments wandenng from untreated to treated areas of gram For No imtial expenmental samplmg was carried out, so the instance, once the gram surface had been disturbed, the peak populations of msect before treatment, were not adults became quite active Mamly adults were trapped at recorded However, the storekeeper's records, pnor to the the start of the test m February but by Apnl larvae were trial, show that nearly 50 msects/trap were bemg caught found most commonly before treatment (Fig 2) Thereafter, the population m all

Table 7. Companson of the average number of P fur per trap at the surface of a gram store m an untreated area (n = 39) , 2 areas treated With pmnuphos-methyl ( n = 2 x 30) and 2 areas treated With etnmfos (n = 2;( 28)

Month February March April May June Week 4 8 12 16 20

adults Untreated 70 17 1 o 2 o 05 P-m 1 1 03 o 4 o 1 o 10 P-m2 1 86 1 26 o 23 o 10 Etnmfos 1 207 o 85 o 07 o 14 o 03 Etnmfos 2 o 85 o 21 o 14 0 o 46 larvae Untreated 9 14 11 5 3 P-m 1 o 93 o 93 136 223 186 P-m2 o 66 1 86 106 o 56 o 86 Etnmfos 1 o 57 1 57 o 92 o 96 o 85 Etnmfos 2 210 3 00 135 o 46 114

not dependent on the activities of other msects transformmg Discussion the gram mto dust There were no infestations of other insects, except for a few psocids and the inevitable low Long-term expenments of infestations m gram storage are numbers of mites The infestations of Ptuius only became far and few between but Coombs and Freeman (1955) found troublesome after 4 - 5 years, which, With their low productivity and slow Me-cycle, was presumably the time both P tectus Boield and P fur m an empty granary and needed for the mfestation to become detectable The suggested the ptmids were hvmg on the dust produced by evidence of dtrect damage to whole gram was apparent but Sitoplulu» qromarius (L ) Coombs and Woodroffe (1963, they presumably also fed on the bodies of other 1968) set up a 7 year, experimental succession m 6kg bulks and each other Damage was also evident on the undersides and P teetus became the dommant msect after S of the wooden duckboards mto which the larvae had bored to grananus had destroyed most of the gram and declmed In form pupation cells a further experiment, over 10 years and in 1 tonne bulks, P teetus survived but never dommated m the presence of Acknowledgements S grananus and Oryzaephtlus sunnamensts The observations m the bulk gram stores show that P fur was Grateful thanks are due to the staff at the gram stores for 56 Proceedmqs of the 7th Iniernaiumal WOl'hng Conference on Stored-product Protection - Volume 1 allowing us to carry out the large-scale tnal, to Russell 46, 399 - 417 Collard, Regional Cereals Officer, HGCA, Paula Doherty, Coombs, C Wand Woodroffe, G E 1963 An Deputy Regional Cereals Officer, HGCA, for her support and expenmental demonstration of ecological succession m an technical advice, to the CSL team of, Terry Bmns, Debbie population breeding m stored wheat Journal of Collms, Chnstme Sruady, Alex Buckland, Peter Clarke and Ecology, 32, 271 - 279 Dean Cook for their tremendous efforts m setting up and Coombs, C Wand Woodroffe, G E 1968 Changes m the momtonng the surface treatment and to Zeneca Crop fauna of an expenmental bulk of stored wheat Protection for donating the pmmiphos-methyl The residue Journal of applied Ecology, 5,563 - 574 analysis was supervised by Alison Lord Trevor Jacob Godan, D 1952 Pimus fur L an Raps und Mohn provided some useful references and Alex Buckland earned Zei tschnft hygemische Zoologie, 40, 289 - 296 out the bioassay Howe, R W 1959 Studies on beetles of the family The work was funded by Pesticide Safety Directorate and Ptimdae 17 Conclusions and additional remarks Bulletin Arable Crops Group M A F F of Entomological Research, 50, 287 - 326 Howe, R Wand Burges, H D ,1951 Studies on beetles References of the fanuly Ptnudae VI- The biology of Ptmus fur (L) and P sexpunctaius Panzer Bulletm of Braune, R 1948 Comparative research on the parasitic Entomological Research 42,499 - 511 beetles, Ptmus tectus Boield, Ptmus fur, L,Pimus Pnckett, A J 1994 Animal Feed Mills 1992 England and latro Fabr , Piinus sexpunctatus Panz and Pimus Wales Pest Management Parts 1 & 2 Central SCience brunueus Duft, With an expenmental proof of the Laboratory Rep 5473 + 74 pp Mnustry of Agriculture, necessity for mamtammg the fhnd balance m the body of Fisheries and Food, Slough, UK insects Zeitschnft Morphologic und Ecology Tiere 39, Pnckett, A J and Muggleton, J M 1991 Commercial 546 - 691 (In German) gram stores 1988/9 England and Wales Pest incidence Cogan, PM, Wakefield, M E and Pmruger , D B and storage practice H G C A Project Report 29, 99pp (1992) PC, a novel and inexpensive trap for the detection Home-Grown Cereals Authonty, London of beetle pests at low densities m stored gram In Woodroffe, G E 1953 An ecological study of the insects and Proceedmgs 5th International Workmg Conference Stored mites m the nests of certain birds m Bntam Bulletm of - Products Protection F Fleurat-Lessard & P Ducom Entomological Research, 44, 739 -772 Eds II, 1321-1329 Zakladnot and Ratanova, V F 1987 Stored gram pests and Coombs, C Wand Freeman J A 1955 The insect fauna their control Oxonian Press, New Delhi 268pp of an empty granary Bulletin of entomological Research

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