S. bifasciatus  is a common species that can be found throughout the Netherlands, with exception of the provinces Zeeland and Groningen where the species is rare [2,3].
The species is active from May until half September [2,3].
S. bifasciatus nests usually in hollow stemms, but may be found in walls (also of buildings) and dead wood . She uses bee hotels as well and can be found in galls of the grass fly genus Lipara (CHLOROPIDAE) .
The female normally fills a nest cel with one prey, but sometimes two or more prey specimen are used when there is an abundance .
The female applies an adaptive strategy when building nests, so that the length of the cell is changed based on the diameter of the bore hole . The resulting cel has effect on the sex of the wasp that develops in that longer cells will produce more and heavier females . There is no effect on males .
Also the larger the number of cells in a nesting cavity the less females will be produced. Older females will construct less cells and provide less provisions, and from those cell less females will develop .
The wasp uses artificial nest help and has a preference for :
– nest blocks located at 1 to 2 meters in height
– nest blocks with an orientation north or west (hypotheses), she uses nest blocks with southern or eastern orientation as well
– bore holes 3-4 mm in diameter
2.3. FOOD PLANTS
Adult S. bifasciatus wasps feed with necter and/or pollen. In literature the following plant species and groups are mentioned :
|Apicaceae||Pastinaca sativa |
Research has shown that prey is found in different tree species and that S. bifasciatus is flexible in finding appropriate prey sources. The following trees have been identified:
|Populus tremula |
|Salix sp. |
|Alnus incana |
As far as I know these trees are not in the vicinity of the garden, which may explain that I only found the species once so far.
The species is narrow oligophagous on beetlelarvae from the family of leaf beetles (CHRYSOMELIDAE) . Literatuur mentions the following species that occur in the Netherlands:
|CHRYSOMELINAE||– Plagiosterna aenea (Linaeidea aenea) |
– Phratora laticollis 
– Phratora vitellinae 
– Phratora vulgatissima 
– Plagiodera versicolora 
The following nest parasites on S. bifasciates are mentioned in literature:
|– Chrysis ignita [3,8]|
– Chrysis angustula 
– Chrysis viridula (gezien bij nesten) 
|– Melittobia acasta |
The following of these parasites have been observed in the garden:
|– Chrysis ignita|
Length males: 7 – 11 mm
Length females: 7 – 11 mm
Symmorphus can be recognized by the longitudinal groove on tergite 1 . It also has a medial keel on tergite 1, a characteristic it shares with the genus Ancistrocerus.
♀ & ♂
2. Thorax with short hairs, hairs on top (mesonotum) dark, hairs sides (mesopleura) light 
3. Pronotum with continuous keel from reaching the tip 
4. Antennal shaft black 
7. Tergites 1, 2 and 4 with yellow band, tergite 3 sometimes with yellow spot 
The variant S. bifasciatus eumenoides has two yellow kidney-shaped spots on tergite 2 .
8. Top part mesopleuron, above transverse groove, with large and deep pits, the space between the pits is smaller than pit diameter. 
9. Vertical part tergite 1 shorter than the horizonal part
1. Antenna with 12 segments 
1. Antenna with 13 segments 
2. Antennal segment 13 as long as wide 
References1 Nederlands Soortenregister
3 Peeters, T.M.J., C. van Achterberg, W.R.B. Heitmans, W.F. Klein, V. Lefeber, A.J. van Loon, A.A. Mabelis, H. Nieuwen-huijsen, M. Reemer, J. de Rond, J. Smit, H.H.W. Velthuis, 2004. De wespen en mieren van Nederland (Hymenoptera: Aculeata). – Nederlandse Fauna 6. Nationaal Natuurhistorisch Museum Naturalis, Leiden, knnv Uitgeverij, Utrecht & European Invertebrate Survey – Nederland, Leiden.
4 Budrienė, Anna. (2003). Prey of Symmorphus Wasps (Hymenoptera: Eumeninae) in Lithuania. Acta Zoologica Lituanica. 13. 306-310. 10.1080/13921657.2003.10512686.
5 BUDRIENE, Anna. Reproductive ecology and behaviour of predatory wasps (Hymenoptera: Eumeninae). Doctor al thesis. Vilnius, 2004.
6 AMOLIN, A. V.; OGOL, I. N. Ïèùåâûå ñâÿçè ñêëàä÷àòîêðûëûõ îñ (Hymenoptera: Vespidae) ñ öâåòêîâûìè ðàñòåíèÿìè (Magnoliophyta) â Äîíáàññå Trophic relations of wasps (Hymenoptera: Vespidae) with flowering plants (Magnoliophyta) in Donbass.
7 SCHMID-EGGER, C. H. Bestimmungsschlüssel für die deutschen Arten der solitären Faltenwespen (Hymenoptera: Eumeninae). Deutscher Jugendbund für Naturbeobachtung, 1994, 54: 90.
8 PEREIRA‐PEIXOTO, MARIA HELENA, et al. Diversity and specificity of host‐natural enemy interactions in an urban‐rural interface. Ecological Entomology, 2016, 41.3: 241-252.