Southwestern Association of Naturalists

Insect Pollination of Prickly-Pears (Opuntia: Cactaceae) Author(s): Bruce D. Parfitt and Charles H. Pickett Source: The Southwestern Naturalist, Vol. 25, No. 1 (Jan. 30, 1980), pp. 104-107 Published by: Southwestern Association of Naturalists Stable URL: http://www.jstor.org/stable/3671218 Accessed: 13-11-2015 20:21 UTC

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Fig. 1. Nests of Osprey (upper) and Great Blue Heron in cardon cactus, Tiburon Island, Sonora, May 1978. almost immediately. The heron returned within a few minutes and attempted to alight on its nest. It made three attemptsby approaching from above and passing over or alongside the Osprey nest. In each case it was driven off by the Osprey. On its fourthattempt it approached the nest fromthe frontand below, apparently not disturbingthe Osprey, and was permittedto settle on its nest. Both species are known to use an extremelywide assortmentof nest sites includ- ing the ground, cliffs,shrubs, and trees. Bent (1937) stated, for Ospreys, that, "Security and a good food supply seem to be all that they require," and that the Great Blue Heron prefers "to nest in trees and usually selects the tallest trees available; but often nests in low trees, or bushes, or even on the ground" (Bent 1926). On Tiburon Island, cardons provide the tallest and most substantial nest sites, and the waters of the adjacent bay apparently supply the necessary food supply. I wish to thank Clyde Jones, U.S. Fish and Wildl. Serv., and the U.S. Nat. Park Serv. for supporting this U.S./Mexico cooperative project.-Roland H. Wauer, National Park Service, Washington, D. C. 20240.

INSECT POLLINATION OF PRICKLY-PEARS (OPUNTIA: CACTACEAE). -In conjunction with breeding studies of Opuntia, we attempted to determine the primary insect pollinators 1 mi S Mineral Park, in the Cerbat Mountains SE Santa Claus, Mohave Co., Arizona. On 9-10 Jun. 1978, the flowerson one plant each of Opuntia chlorotica Engelm. & Bigel. and Opuntia phaeacantha Engelm. var. discata (Griffiths)Benson & Walk- ington were observed from 0810-0910 MST, and a differentindividual of each

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This content downloaded from 156.40.216.1 on Fri, 13 Nov 2015 20:21:54 UTC All use subject to JSTOR Terms and Conditions was observedfrom 0925-1025 MST. On the secondday the observationswere re- peatedusing differentindividuals of the same taxa. Flowerscommenced to open early in the firsthour of observationand began to close late in the afternoon, about1600 MST, ofthe same day. An attemptwas made to capture all insectsvisiting the flowersduring the scheduledtimes. The insectswere capturedby placing a small glassinebag over the flower.Sap beetles (Nitidulidae) could not be easily capturedupon entering a flowerand were collectedlater (1500 MST) by placing an entireflower into a standardinsect kill-jar. At our studysite the Anthophoridae(Diadasia sp.), the Halictidae (Halictus sp., Lasioglossumspp., and Augochlorellasp.), and the Megachilidae(Ashmeadi- ella sp.) were represented;the Apidae were not (Table 1). In contrastto other studies,we foundthe Megachilidaeto be the least commonof the visitingbees. Beutelspacher(Cactaceas y SuculentasMexicanas 16:84-86, 1971) reportedMeg- achile sp. (Megachilidae) to be an importantpollinator of Opuntia spp. in the Valley of Mexico, with Apis melliferaL. (Apidae) and Lasioglossumsp. less common.Cockerell (Am. Nat. 34:487-488,1900) discussedLithurge spp. (Meg- achilidae) of New Mexican Opuntiaand Echinocactusflowers. In additionto bees,we foundsap beetlesin large numbers,and a single leaf- footedbug (Coreidae) was foundin-flower, its occurrenceprobably incidental. The large anthophorids(Diadasia sp.) visitedthe flowersfor pollen and pro- bably fornectar as well. They land upon the stigmaor anthersand walk on the anther"platform" around the stigmaas they collectpollen. These bees are suffi- cientlylarge that,while walkingon the limitedspace providedby the platform, a pollen-loadedleg is in continualcontact with the stigma.Thus fromour ob- servations,these are importantinsects for transferring pollen to the stigma.We collecteda small anthophorid(Ceratina nanula Cockerell) which, althougha pollen collector,is not an effectivepollinator because its size is such that it may walk upon the antherplatform without its legs necessarilycoming in contact withthe stigma. The large anthophoridsappear selectiveas to which flowersthey visit.About half as many actuallyland on the flowersas flypast the plant. The non-visitors pause brieflyabove each flowerbefore continuing on to anotherplant. Oftenthe same bee fliesfrom the flowersof one speciesof Opuntiato thoseof another,and the same speciesof Diadasia was foundin the season'searliest flower of Ferocactus acanthodes(Lemaire) Britt.& Rose var. Lecontei(Engelm.) Lindsay. Small solitarybees (Megachilidae and Halictidae) are apparentlysomewhat less importantas pollinators.The megachilidscollect pollen on the abdomenwhile somehalictids carry great masses of pollenon theirlegs. These small bees almost always land on the anthersor adjacentperianth, and usually leave withouthav- ing come in contactwith the stigma.However, occasionally they land on the stigmabefore quickly moving to the anthers.We were unable to distinguishthe twofamilies of small bees in thefield. Nitidulids,the mostcommon insects in the flowers,appear to be the least im- portantas pollinators.Almost always they land upon the perianthor anthersand move immediatelyto the bases of thesestructures where they mate and probably feedupon nectar.Only rarelydo theycome in contactwith the stigma.Although they flyto flowerson differentplants, sap beetleshave no pollen carryingap- paratusand pollen does not adherewell to theirbodies. The obviousdecline in

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This content downloaded from 156.40.216.1 on Fri, 13 Nov 2015 20:21:54 UTC All use subject to JSTOR Terms and Conditions TABLE 1. Pollinator visits to two Opuintia species in the Cerbat Mountains, Arizona. 9 June 10 June 8:10 9:25 8:10 9:25 x Insects/Flower

No. of Flowers 4 4 3 5 Opuntia Anthophoridae1: Diadasia sp. 3 0 3 1 0.4 chlorotica Megachilidae: Ashmeadiella sp. 0 0 0 1 0.1 Halictidae: 11 8 6 14 2.4 Lasioglossum (Dialictus) spp. 11 6 3 11 1.9 Halictus tripartitus 0 2 2 3 0.4 Augochlorella sp. 0 0 1 0 0.1 Small Bees2 0 3 10 6 1.2 x Bees/Flower 3.5 2.8 6.3 4.4 4.1 Nitidulidae 166 171 82 134 x Beetles/Flower 41.5 42.8 27.3 26.8 34.6 Opuntia No. of Flowers 6 4 3 5 phaeacantha Anthophoridae: Diadasia sp. 2 3 5 2 0.7 var. discata Megachilidae: Ashmeadiella sp. 0 3 0 0 0.2 Halictidae: 9 9 5 2 1.4 Lasioglossum (Dialictus) spp. 7 7 5 2 1.2 Halictus tripartitus 0 2 0 0 0.1 Augochlorella sp. 2 0 0 0 0.1 Small Bees 0 1 0 3 0.2 Bees/Flower 1.8 4.0 3.3 1.4 2.4 Nitidulidae 79 110 48 94 x Beetles/Flower 13.2 27.5 16.0 18.8 18.4 1 We thank Charles D. Michener, University of Kansas, Lawrence, for insect identifications. 2 Small bees, Megachilidae or Halictidae, which escaped and therefore could not be furtheridentified.

This content downloaded from 156.40.216.1 on Fri, 13 Nov 2015 20:21:54 UTC All use subject to JSTOR Terms and Conditions beetlepopulations on 10 Jun. (Table 1) undoubtedlyreflects the increasedwind velocitythat day. Opuntiachlorotica was near a ridge-top,where the especially gustywinds doubtless made flight difficult for the small beetles. The flowersof the prickly-pearsstudied are apparentlyadapted to pollinationby large bees,such as Diadasia, while small bees and sap beetlesare largelythieves. The stamensof the opuntiasstudied are mobileand, when sufficientlystimulated, moveinward and tightlyenclose the style.Sap beetlesand small bees do not have sufficientstrength or weight to initiate a response,but we observedthat the Diadasia species is capable of stimulatingthe stamenssufficiently. It may be that a large bee workingits way to the nectarat the base of the stylecauses the stamensto close,and is forcedto exit past the stigmawhere pollen is deposited duringthe struggleto escape.While guidingthe bee past the stigma,the anthers also depositpollen on the insect'sbody (Beutelspacher1971). Because in our study small bees infrequentlycontacted the stigma,thigmotrophic behavior of the stamenstakes maximumadvantage of the infrequentvisits by large bees.- Bruce D. Parfitt and Charles H. Pickett, Dept. Botany and Microbiology, Arizona State Univ., Tempe, AZ 85218.

OBSERVATIONS ON AQUATIC COLUBRID SNAKES IN TEXAS.-In this paper we reportlaboratory and fieldobservations on severalspecies of snakesof the generaNerodia and Regina in easternTexas. Regina grahamihas been ob- servedutilizing crayfish burrows (Strecker, Baylor Univ. Mus. Contrib.4:3-11, 1926; Anderson, The reptiles of Missouri, Univ. Missouri Press, 1965; Mushinsky and Hebrard,Herpetologica 33:162-166, 1977), but the species has never been reportedas a mud-burrower.On 22 Jul. 1977,a R. grahamiwas capturedat night on a tree limb approximately75 cm above the surfaceof the Navasota River, Brazos Co., Texas. The animal was kept in a 10-gallonaquarium partitioned into equal areas of water and soil. On severaloccasions the snake was observed excavatingburrows, and burrowingwas initiatedboth underwaterand atop the soil. Burrowingusually resultedin the excavationof a chamberbeneath the water level into which the snake would withdrawits entirebody. Breathing was accomplishedby the snake extendingonly its nostrilsand eyes above the water forshort periods of time. On the firstday of introductioninto the aquari- um, extensionof the head fromthe burrowoccurred about every 5 min. How- ever,several days later,the animal would remainwithin the chamberfor about 45 min beforeextending the head to breath.The maximumperiod of submergence without respiration was 46 min. Nerodia erythrogasterand N. rhombiferahave been reportedto remain underwaterfor 26 min and N. fasciata for 24 min (Jacob and McDonald, Comp. Biochem.Physiol. 53A:69-72, 1976). Afterintro- ductioninto the aquarium,the R. grahamiwas not observedout of its burrowfor 7 days.A pregnantN. fasciataconfluens also was maintainedin a separateaquari- um with similarsoil and water conditions,but burrowingbehavior was not ob- served.Crayfish-burrow utilization by a single N. fasciatahas been reportedby Kofron(J. Herpetol.12:543-554, 1978). The R. grahamibore 16 young on 11 Sep., and the N. fasciatasix young on 20 Sep. 1977. The N. fasciatagave birthupon soil, and several neonatesshed within1 h afterbirth. On the firstday the youngN. fasciatacould not be induced to bite, but strikingwas elicitedthe second day. The vibrationsof fingernails

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