428 KB22 KB199320242013Grad, Janezštevilka:1letnik:21str. 17-28COBISSID:1225461ISSN:1318-1998URN:URN:NBN:SI:doc-CKDNH4GCslPrirodoslovni muzej SlovenijeSlovensko entomološko društvo Štefana MichielijaActa entomologica slovenica (Ljubljana)Bombusbumblebeesčmrljifavnaforaging behaviourfrekvenčna porazdelitevfrequency distributionizletavanje na pašoSloveniaSlovenijaDnevno izletavanje čmrljev na pašo|A daily foraging frequency distribution of six different species of bumblebees is described and analysed. The counting of B. hypnorum was carried out on a chosen sunny day in May 2009, when the number of workers of the observed nest approached its maximum. The species is known as having a very short life cycle. The counting of B. lapidarius (two nests), B. pascuorum, B. humilis (two nests), B. sylvarum and B. hortorum was carried out in approximately two weeks intervals during the period between June and September 2012 or until the visible reduction of foraging activity of some species. There was a partly sunny weather with frequent showers on the first day of observation, but the bumblebees successfuly overcame that. Within the following observation days the weather was sunny and warm. The following interesting findings and conclusions were reached: (1) Some species of bumblebees, for instance B. humilis, start foraging much later in the morning than some other species, for instance B. hypnorum; (2) In nests with a larger number of workers, foraging in the morning hours occurs in groups of two to five workers within a few minutes, with periods up to several minutes when not a single worker leaves the nest. (3) Despite somewhat different foraging frequency distribution in different bumblebee species, the cumulative frequencies during the entire period of observation were similar in all species, except in B. hortorum: the number of flights was on the increase from the morning towards early afternoon, and slowly decreased afterwards until coming to an end in the evening. In B. hortorum two maximum peaks are noticeable, one in the morning hours and one in the eveningPrikazana in analizirana je porazdelitev pogostnosti izletavanja na pašo delavk več vrst čmrljev. Štetje delavk družine B. hypnorum je bilo opravljeno na izbran dan v mesecu maju leta 2009, ko se je družina približevala vrhu razvoja v svoji značilno kratki življenjski dobi in se je število delavk v njej bližalo svojemu maksimumu. Štetje delavk čmrljev B. lapidarius (dve družini), B. pascuorum, B. humilis (dve družini), B. sylvarum in B. hortorum pa je bilo opravljeno v približno dvotedenskih presledkih v času od junija do septembra leta 2012, oziroma do opaznega zmanjšanja števila izletelih delavk pri določenih vrstah v mesecu avgustu. Vreme na prvi dan opazovanja je bilo delno sončno z več močnimi plohami, v vseh drugih dneh pa je bilo toplo in celo vroče od jutra do večera. Zanimive ugotovitve so bile: (1) da nekatere vrste, na primer B. humilis, pričnejo zjutraj izletavati precej kasneje od nekaterih drugih vrst, na primer B. hypnorum; (2) da izletavanje delavk v jutranjih urah pri močnejših (številčnejših) družinah poteka v skupinah, s po dve do pet delavk v posamezni skupini, v času nekaj minut, z večminutnimi presledki med zaporednimi skupinami, ko ne izleti nobena delavka (na primer pri B. lapidarius); (3) da je, kljub drugačnim porazdelitvam izletavanja pri posameznih opazovanjih, skupna (sešteta) porazdelitev izletavanja skozi vse opazovano obdobje za vse vrste, razen za B. hortorum, podobna: število izletov raste od jutra proti popoldnevu, ko doseže maksimum, nato pa proti večeru počasi upada. Pri B. hortorum je izletavanje približno enakomerno skozi ves dan, z opaznim jutranjim in večernim porastom števila letovTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaPrirodoslovni muzej Slovenije