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Andrena knuthiana Cockerell, 1901
Andrena knuthiana_homonym Cockerell, 1901, correct original spelling; Andrena knuthina Cockerell, 1901, incorrect original spelling

Life   Insecta   Hymenoptera   Apoidea   Andrenidae   Andrena
Subgenus: Thysandrena

Andrena knuthiana FEM CFP
© Copyright Laurence Packer 2014 · 7
Andrena knuthiana FEM CFP

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Andrena knuthiana MALE CFP
© Copyright Laurence Packer 2014 · 7
Andrena knuthiana MALE CFP
Andrena knuthiana, face
Smithsonian Institution, Entomology Department · 1
Andrena knuthiana, face

Andrena knuthiana, side
Smithsonian Institution, Entomology Department · 1
Andrena knuthiana, side
Andrena knuthiana, top
Smithsonian Institution, Entomology Department · 1
Andrena knuthiana, top

Andrena knuthiana, wing
Smithsonian Institution, Entomology Department · 1
Andrena knuthiana, wing
Overview
Reprinted with permission of the American Entomological Society from: LaBerge, W. E. 1977. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VIII. Subgenera Thysandrena, Dasyandrena, Psammandrena, Rhacandrena, Euandrena, Oxyandrena. Transactions of the American Entomological Society 103: 1-144.

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This small western bee is closely related to Andrena w-scripta from which it can be distinguished by the much coarser clypeal punctation as described below and the darker vestiture, especially of the terga.

FEMALE. MEASUREMENTS AND RATIOS. — N = 20; length, 8-10 mm; width 2.5-3.0 mm; wing length, M = 3.35 ± 0.140 mm; FL/FW, M = 0.97 ± 0.006; FOVL/FOVW, M = 3.30 ± 0.048.

INTEGUMENTAL COLOR. — Black except as follows: mandible with apical half or less rufescent; flagellar segments 3-10 dark reddish-brown to black below; tegulae dark; wing membranes clear, hyaline, veins dark brown to black; distitarsi dark; tibial spurs yellow.

STRUCTURE. — Antennal scape and flagellar segments as in w-scripta. Eyes each about four to four and one-fourth times as long as broad, inner margins parallel or converging extremely slightly towards mandibles. Malar space, mandibles and galea as in medionitens and w-scripta. Maxillary palpus as in medionitens but segmental ratio about as 1.0:1.0:0.8:0.8:0.7:0.7. Labial palpus as in medionitens but ratio about as 1.0:0.5:0.4:0.5. Labrum as in candida, process usually weakly emarginate apicomedially. Clypeus only slightly flattened medially, with deep, round, large punctures separated mostly by half to one puncture width or less, smaller peripherally, midline usually not impunctate, surface shiny apicomedially to shagreened basally. Supraclypeal area as in candida. Genal area as in candida, at most moderately shiny. Vertex and face above antennal fossae dull, tessellate, face finely rugulate as in w-scripta and candida. Facial fovea broad and shallow as in candida and w-scripta, separated from lateral ocellus by less than one ocellar diameter (about as 7:8 or 9).

Pronotum as in candida. Mesoscutum with punctures small and sparse, more crowded and anteriorly and laterally, surface moderately shiny to dull, fine reticular shagreening present throughout or absent or weak only posteromedially. Scutellum similar to mesoscutum but usually shinier. Propodeum and mesepisterna as in w-scripta or candida. Wings as in medionitens.

Metasomal terga, pygidial plate and sterna as in w-scripta; terga with punctures often not evident, always dulled by fine reticulotransverse shagreening.

VESTITURE. — As in candida and w-scripta except as follows: pale hairs usually white (often pale ochraceous on thoracic dorsum); vertex dark brown; facial foveal hairs and hairs along inner margins eyes brown; mesoscutum posteromedially and scutellum usually with at least a few dark hairs mixed with the pale ochraceous; tergum 4 with apical pale fascia usually narrowly interrupted medially, occasionally complete, that of terga 2 and 3 always interrupted medially; terga 5 and 6 with brown to black hairs; sternal hairs mostly brown; fore and middle tibiae with other surfaces dark brown; tibial scopal hairs white, often dark brown below pygidial plate.

MALE. MEASUREMENTS AND RATIOS. — N = 20; length, 7-9 mm; width, 1.5-2.5 mm; wing length, M = 2.95 ± 0.155 mm; FL/FW, M = 0.97 ± 0.007; FS1/FS2, M = 1.05 ± 0.023.

INTEGUMENTAL COLOR. — Black as in w-scripta except as follows: clypeus showing a small amount of yellow medially in one specimen; terga with apical areas only slightly translucent; wing veins dark brown to black flagellum dark brown below.

STRUCTURE. — Antennae short, in repose barely reaching metascutum scape length and flagellar segments as in w-scripta. Eyes, malar space, mandibles and galea as in candida. Maxillary palpus as in medionitens but segmental ratio about as in female. Labial palpus as in medionitens but ratio about as 1.0:0.5:0.5:0.5. Labral process as in candida. Clypeus as in female but punctures smaller, usually distinctly coarser than in w-scripta but occasionally about same, surface usually shiny. Supraclypeal area, genal area, vertex and face as in female.

Thoracic sculpturing as in female but mesoscutum more often shiny except in narrow anterior area and propodeum with dorsal area often minutely roughened mediobasally.

Metasomal terga much as in female. Sterna as in medionitens or w-scripta. Sternum 6 flat, emarginate apicomedially. Terminalia as in Figures 32-36.

VESTITURE. — Generally as in candida or w-scripta but usually with considerably more dark brown hairs. Head hairs often mostly dark; mesoscutum and scutellum with at least a few dark hairs medially; terga 6 and 7 and usually 5 entirely dark brown, rarely brown medially and paler laterally; terga 2 to 4 or 2 to 5 with apical pale fasciae white and interrupted medially and usually with short brown hairs basally. Sterna 2-5 with well-formed, pale fimbriae of moderately long, often curved hairs, basal hairs occasionally brown. Sternum 6 normally hairy, not densely so, often dark brown.

REMARKS. — Males of knuthiana are very difficult to separate from those of w-scripta because of variation in size of clypeal punctures in either species and because of variation in the vestitural hair color in both species. Generally, a male with coarse clypeal punctures also has dark tergal vestiture (especially on terga 6 and 7). This is typical of knuthiana. Specimens with the clypeal punctures very coarse and the vestiture paler have also been considered as knuthiana as are specimens with moderately coarse clypeal punctures and dark tergal vestiture. Only the males with both pale vestiture and fine clypeal punctures are left in w-scripta. This system probably means that a low percentage of males are misidentified (perhaps 5 to 10%), being labeled incorrectly as knuthiana. However, without additional characters, I believe that this is the best arrangement.

It is also possible that the two species are hybridizing with most hybrids being classified as knuthiana under this system. However, the two species seem to be distinct in the female sex without undue mixing of characters, although they are sympatric over much of the range of knuthiana.

Andrena knuthiana is also closely related to and easily confused with the two species described immediately following. The distinctions between knuthiana and these two species are given in the diagnoses of the latter.

Names
Scientific source:

Supported by

Hosts · map
FamilyScientific name @ source (records)
Freilich, j.  1545 @ JRYA__OLYM (1)
Lauraceae  Persea americana @ UCRC_ENT (1)
Onagraceae  Oenothera @ AMNH_BEE (1)
Rhamnaceae  Ceanothus sp @ AMNH_BEE (1)

Ceanothus @ AMNH_BEE (1)

Rhamnus californica @ BBSL (1)
Rosaceae  Adenostoma fasciculatum @ AMNH_BEE (1)

Prunus virginiana @ BBSL (1)
_  Withheld @ BBSL__YOSE (1)

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Updated: 2024-03-28 19:12:22 gmt
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