Crossocerus annulipes 
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Latin: having a ring-shaped foot
3. Plant relations
4. Prey relations
5. Parasitic relations
Crossocerus annulipes is an uncommon wasp  that occurs spread throughout the Netherlands [3,9] , but is not present in meadows and polder areas, and on the wadde islands .
The species is active from end april to half october .
The females built their nests in rotting wood like tree stemms and tree trunks [4,5]. They gnaw the nests themselves or use old beetle tunnels that are extended . After 5-10 cm the main corridor branches into side corridors , which are about 3 to 5 cm deep. In each corridor there are no more than two brood-cellls  that are filled with 12 to 25 prey specimen [4,5], usually with 16 . When the brood-cell is filled one egg is positioned on one of the prey specimen . In total the nest can contain 12-20 brood-cells .
Each brood-cell is closed with a plug of chewed wood [4,14].
The time for the small (1,2×0,3 mm)  white  eggs is unknown.
2.3. BEE HOTEL
The males can be found on and around the bee hotels. Regularly they will enter a nest hole and sit the opening looking out, and I suspect they use the hotel to sleep during the night.
The females nest in decayed wood and although they do show interest in the artificial nests I have yet to observe one use them. In 2020, three females had created their nests in a deep crack in the side of one of the nestblocks at ±2m height (section III, block 7). The wasps seemed to enter almost at the same spot but I think they had a different entrance although I have not been able to directly observe it.
Sawdust collected in a small mount at the entrance and on occasion a wasp would take a mouth full into the nest, presumably to plug a nest cell. The sawdust was transported using the jaws. I observed on occasion a wasp bringing prey home of an unidentified Cicadellidae.
One of the wasps was collected for identification.
Most Crabronidae females produce one generation per year .
The caught prey is transported belly-to-belly to the nest .
3. PLANT RELATIONS
The following wood types are mentioned in literature as medium for the wasp to built her nests in:
|Platanus (Plane) |
|Prunus (Peach) |
|Quercus (Oak) |
|Ulmus (Elm) [5,13]|
The adult wasps feed with nectar. The following plants species and groups are mentioned in literature:
The garden contains some umbellifers but I have not yet observed the species on them.
4. PREY RELATIONS
The species does not have a prey preference .
The following species and group occuring in the Netherlands  are mentioned in literature:
adults as well as nymphs 
– Alebra albostriella 
– Elymana sulphurella 
– Edwardsiana rosae 
– Empoasca apicalis 
– Empoasca fabae 
– Eupteryx aurata 
– Eurhadina concinna [6 ( as Eupteryx concinna ) ]
– Kyboasca bipunctata 
– Ribautiana ulmi [6 ( as Typhlocyba ulmi )]
– Ribautiana tenerrima [6 ( as Typhlocyba tenerrima ) ]
– Typhlocyba quercus 
adults as well as nymphs 
None of the mentioned prey species have been observed yet in the garden but there are many Cicadellidae and Meridae.
5. PARASITIC RELATIONS
I have not found any literature references to nest parasites that also occur in the Netherlands.
Length males: 4,5 – 6 mm
Length females: 5 – 7 mm
Het genus Crossocerus can be recognized by the following characters:
1. Small to medium sized species, usually smaller than 10mm (here ±7 mm, female) 
2. Front wing with one submarginal cell [9,10,11]
3. Front wing submarginal cell and discoidal cell separated by vein [9,10,11]
4. Length stigma shorter than length raidal cell [9,11], stigma nnarrow 
5. Veins hind wing clear 
6. Dorsal side thorax (mesonotum) smooth or punctated (here punctated) 
7. Side thorax (mesopleuron) smooth or finely and widely spread punctated [10,11] (here finely and widely spread punctated)
8. Side thorax (mesopleuron) without precoxal keel (verticaulus) in front of middle coxa, at most with small protruding tooth  (here smooth)
9. Rear part side thorax (metapleuron) entirely or partially smooth, at most finely striped (here entirely smooth) 
10. Propodeum without protrusions [9,11]
11. Dorsal field propodeum entirely or for most part smooth, at most very finely striped (here smooth) [10,11]
12. Inneredge eyes stronly converging downwards [9,10,11]
13. Inneredge eyes without indentations [9,11]
14. Distance antenna base to inneredge eye smaller than antenna base diameter [10,11]
15. Ocelli shaped in acute triangle [9,10,11], or almost isosceles 
16. First abdominal segment not petiolate 
17. Length first abdominal tergite max 1,5x width apically [9,11]
18. Abdomen entirely black or with yellow markings (here entirely black) [9,10,11]
- Antenna with 12 segments [9,10,11]
2. Abdomen with 6 segments [9,10,11]
1. Clypeus, frons [9,10] and inner edge eyes  black
2. Clypeus with tow clear teeth [9,10,11]
3. Mandible apically with 3 teeth, innere edge usually without tooth (here without tooth) [9,10,11]
4. Occipital carina ending with spine 
1. Pronotum edges rounded [10,11]
2. Base thigh front leg angular 
3. Outside tarsus member 1 front leg with clear thorn row [9,10,11]
4. Dorsal field propodeum limited by clear furrow [9,11]
- Abdomen black, at most pygidium redbrown [9,10,11]
2. Tergite 2 and 3 without restriction at the base [10,11]
3. Pygidium with concave sides [9,10,11]
4. Pygidium glossy and with well defined frame, not 3-lobed [9,10,11]
5. Tergiet 6 with some hairs next to pygidium [10,11]
- Antenna with 13 segments [9,10,11]
2. Abdomen with 7 segments [9,10,11]
1. Occipital carina ending in clearly angular , ending thornlike , wide with clear tooth 
2. Final antennal segment apically truncated 
3. Clypeus black 
1. Thorax entirely black 
2. Pronotum sides without tooth 
3. Dorsal field propodeum limited by furrow [9,10]
4. Shin (tibia) front leg enlarged towards the tip, with erect bristles [9,10]
5. Tarsal member 1 frint leg enlarged and flattened, clearly wider than tarsal member 1 middle leg 
6. Tarsal member 1 front leg widened, the next two members (2, 3) clearly widened and flattened [9,10]
7. Tarsal member front leg strongly enlarged, yellow with 2 to 3 darker spots [9,10,11]
Shin (tibia) hind leg:
8. Black 
9. Not enlarged
10. Outside often with clear and long thorns 
11. Base trochanter and thigh (femur) front leg with angular protrusion 
1. Abdomen entirely black [9,10,11]
2. Tergites 2 and 3 without constriction at base [10,11]
Here there is a light contriction.
In case of constriction, in C. acanthophorus, there is a clear dorsal narrowing which makes tergite 1 look like it is humped, in lateral view.
3. Tergite 7 not stronger punctated than tergite 6 [9,10]
[DOLLFUSS]: Tergite 7 no visible punctation 
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 Blösch, M. (2000). Die Grabwespen Deutschlands – Lebens‐weise, Verhalten, Verbreitung. 71. Teil. In Dahl, F.: Die Tierwelt Deutschlands. Begr.: 1925. – Keltern (Goecke & Evers). – 480 S. 341 Farbfotos. ISBN 3‐931374‐26‐2 (hardcover). DM 98,–. Zool. Reihe, 78: 353-353. https://doi.org/10.1002/mmnz.20020780208
5 MICHENER, Charles D. Notes on crabronine wasp nests. Journal of the Kansas Entomological Society, 1971, 44.3: 405-407.
6 Hamm, A. & Richards, O.. (2009). The biology of the British Crabronidae. Transactions of the Royal Entomological Society of London. 74. 297 - 331. 10.1111/j.1365-2311.1926.tb02241.x.
7 Ruchin, Alexander & Antropov, Alexander. (2019). Wasp fauna (Hymenoptera: Bethylidae, Chrysididae, Dryinidae, Tiphiidae, Mutillidae, Scoliidae, Pompilidae, Vespidae, Sphecidae, Crabronidae & Trigonalyidae) of Mordovia State Nature Reserve and its surroundings in Russia. Journal of Threatened Taxa. 11. 13195-13250. 10.11609/jott.4188.8.131.5295-13250.
8 KURCZEWSKI, F. E.; MILLER, R. C. Observations on some nests of Crossocerus (Blepharipus) A. Annulipes (Lepeletier and Brulle)(Hymenoptera: Sphecidae). Proceedings of the Entomological Society of Washington, 1986, 88.1: 157-162.
9 KLEIN, Wim. De graafwespen van de Benelux. Jeugdbondsuitgeverij, Utrecht, 1996, 1-130. + KLEIN, Wim. De graafwespen van de Benelux: supplement. Jeugdbondsuitgeverij, 1999.
10 JACOBS, H. J (2007): Die Grabwespen Deutschlands Ampulicidae. Sphecidae, Crabronidae–Bestimmungsschlüssel in Blank, SM & Taeger, A (Hrsg): Die Tierwelt Deutschlands und der angrenzenden Meeresteile nach ihren Merkmalen und nach ihrer Lebensweise, Hymenoptera III–Keltern, Goecke & Evers, 79: 1-207.
11 Hermann Dollfuss, "Bestimmungsschlüssel der Grabwespen Nord- und Zentraleuropas (Hymenoptera, Sphecidae) mit speziellen Angaben zur Grabwespenfauna Österreichs", Publikation der Botanischen Arbeitsgemeinschaft am O.Ö.Landesmuseum Linz, LINZ, 20. Dezember 1991
12 LOMHOLDT, O. 1975-1976; 1984 (2. Auflage). The Sphecidae (Hymenoptera) of Fennoscandia and Denmark. Fauna Entomologica Scandinavica, 4.1: 2.
13 FORMSTONE, Bryan; HOWE, Mike. Brownfield sites and their value for invertebrates–A survey of selected sand quarries in north-east Wales in 2013: Borras Quarry and Marford Quarry.
14 BOHART, Richard M.; BOHART, Richard Mitchell; MENKE, Arnold S. Sphecid wasps of the world: a generic revision. Univ of California Press, 1976.