Supplementary material for the ms:

Title: Nest clumping and nest sharing may not improve brood defense against parasitic flies in a social digger wasp.

Author: Carlo Polidori

Author address: Instituto de Ciencias Ambientales (ICAM), Universidad de Castilla-La Mancha, Avenida Carlos III, s/n, 45071 Toledo, Spain; Tel. 0034-925268800-5480; E-mail:

Table S1. Review of the known Cerceris – Miltogrammini associations, with data on fly behaviour, wasp suggested defensive behaviours, and parasitism rates summarized where available. Factors reducing parasitism include both active (e.g. evasive flights) and passive (e.g. type of prey carriage) behaviours that were observed or suggested by the authors to reduce parasitism rate. Parasitism rate was defined qualitatively based on the authors’ observations on excavated nests, in absence of actual calculations. -: data missing/information not provided.

Host species / Miltogrammine species / Parasitic fly behaviour / Possible factors reducing parasitism / Parasitism rate
C. antipodes Smith 1 / Protomiltogramma plebeia Malloch / Satellite fly / - / -
C. arenaria (L.) 2,3 / Metopia argyrocephala Meigen, Metopia sp. / Hole searcher; infestation of not fully provisioned brood cells / Reduced activity around the site; abandoning parasitized cell; nest temporal co-occupancy by two females / Low, higher in nests with wider entrance2; null3
C. australis Saussure 1,4,5 / Protomiltogramma laticeps Malloch, undetermined sp. / Satellite fly; larviposit on prey as it is being carried into the nest; flies may exploit the occasions in which the guard is shortly retracted deeper into the tunnel to larviposit; in some occasions flies enter the nests and stay 2-3 s; 1-3 flies can follow a single wasp / Evasive manoeuvres / very low
C. bicincta Klug 6 / Pterella melanura (Meigen) / Satellite fly; 1-3 satellite flies can follow a single wasp; flies larviposit on the prey while the wasp is entering the nest; flies perched on small stones / Evasive manoeuvres; face-to-face steady flight with the fly / 30%
C. bicornuta Guerin-Meneville 7 / Senotainia kansensis (Townsend) / Satellite fly / - / -
C. blakei Cresson 8 / Undetermined sp. / - / - / -
C. californica Cresson 9,10 / Amobia floridensis (Townsend), M. argyrocephala, Sentoainia sp. near rubriventris / Hole searcher (Metopia), satellite fly (Amobia, Senotainia) / - / -
C. clypeata Dahlbom 11 / Senotainia trilineata Wulp / Satellite fly / - / -
C. echo Mickel 12 / S. trilineata / Satellite fly; flies follow a small proportions of wasps (4%); half of satellite flights end in contact with prey at the moment of introducing it in the nest; frequently a fly would follow a slow flying wasp for a short distance (<0.5 m) and then return to its perch; daily activities of wasps and flies match / Carrying the prey tucked up under the thorax / -
C. femurrubrum Viereck and Cockerell 13 / Undetermined sp. / Satellite fly / Evasive manoeuvres / -
C. flavofasciata floridensis Banks 14 / Undetermined sp. / - / - / low
C. frontata Say 15 / Metopia sp. / Hole searcher / - / -
C. fumipennis Say 10,14,16,17,18,19,20 / M. argyrocephala, undetermined sp., S. trilineata, Phrosinella fumosa Allen, Phrosinella aurifacies Downes, Sentoainia rubriventris Macquart, S. sp. near rubriventris / Hole searcher (Metopia, Phrosinella), satellite fly (undetermined sp., Senotainia); 1-3 satellite flies can follow a single wasp and larviposit on prey while wasp entering nest (undetermined sp.); hole-searchers do circling flights around nest entrances and then enter nests; rarely, S. trilineata larviposit on the wall of the upper part of the burrow; S. trilineata may also follows the wasp into the burrow for 3-5 s / Evasive manoeuvres; abandonment of parasitezed prey (undetermined sp.); intermix prey stock in the upper part of the tunnel with soil (M. argyrocephala) / 2% (P. fumosa); 10% (P. aurifacies); 10% (S. trilineata); 6% (S. rubriventris) 13% (undetermined sp.)
C. graphica Smith 13 / S. trilineata / Satellite fly / - / -
C. halone Banks 21,22 / M. argyrocephala, Metopia campestris (Fallen), Amobia sp. / Hole searcher (Metopia), satellite fly (Amobia) / Evasive manoeuvres (Amobia) / -
C. nigrescens Smith 23 / S. trilineata / Satellite fly / - / -
C. rubida (Jurine) 24, 25,26 / Pterella grisea (Meigen), Pterella melanura (Meigen), undetermined sp. / Satellite fly; 1-4 satellite flies can follow a single wasp; flies larviposit on the prey while the wasp is entering the nest or into the upper part of the tunnel; daily activity of wasps and flies overlapped; greater activity in higher nest density areas (but not per nest) and on social vs solitary nests (but not per foraging trip) / Evasive manoeuvres; turning and chasing the fly while being followed / 6%
C. rufimana Taschenberg 27 / Senotainia sp. / Satellite fly / - / null
C. rufopicta Smith 19,28,29 / Metopia sp., Phrosinella sp., Senotainia sp., M. argyrocephala, S. trilineata / Hole searchers (Metopia, Phrosinella,), satellite fly (Senotainia sp.); hole searchers visit nests for 12-20 s. Satellite flies contact prey with abdomen while carried in flight / - / null
C. sabulosa (Panzer) 6 / P. melanura / Satellite fly / - / null
C. simplex macrosticta Viereck and Cockerell 10,13 / S. trilineata (probably) / Satellite fly; 72% of foraging wasps followed; flies contact prey held by air-borne wasps; 1-3 females can follow a single wasp / Evasive manoeuvres; diving into the vertical entrance shaft without pausing outside the nest; prey cleaning prior to place them in the cells / 8%
Cerceris spp. 30 / P. grisea / Satellite fly; larvae found on Clythra beetle prey in nests / - / -

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26 Present study

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the Identification of British InsectsVol 10 Part 14. Royal Entomological Society of London, London.

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