Ectemnius cavifrons ♀︎♂︎

Last update: 4 July 2021
SPECIES: Ectemnius cavifrons
GENUS: ECTEMNIUS
FAMILY: Digger wasps (CRABRONIDAE)



OBSERVATION:
2021-VIII-282021-VI-102021-VI-082021-VI-062021-IX-072020-VI-222020-VI-022020-V-212020-V-202020-V-192019-VII-222019-VI-09

YEARS:
201920202021

MONTHS:
JanFebMarAprMayJunJulAugSepOctNovDec


Official name

Synonyms

Ectemnius cavifrons [1]

Clytochrysus cavifrons
Crabro chrysostomus

See also: www.gbif.org

Ectemnius cavifrons ♂︎

CONTENTS

1. Distribution
2. Behaviour
3. Plant relations
4. Prey relations
5. Parasitic relations
6. Identification

1. DISTRIBUTION

The wasp Ectemnius cavifrons [1] is uncommon and occurs throughout the Netherlands [2].

2. BEHAVIOUR

2.1. ACTIVITY

The species is active from half April up to end September [3].

2.2. DEVELOPMENT

Her widely branched nests are gnawed in rotting and dead wood [3,5], but old tunnels from a previous season can also be re-used [5].
A nest location can reside in a completely shades location [9].

The nest starts with a straight corridor that branches after several centimetres in up to thirteen side corridors that can reach 30-70 cm in depth, sometimes even up to 120 cm [5]. At the end of these tunnels a brood cell is located that measures 8-10 (h) x 12-15 (l) cm [5].

Two females may use the same entrance but each will gnaw it’s own corridors [5]. It is also possible that numerous females will nest in a nest aggregation [10].

The larvae are fed flies, about 6-12 prey species per brood cell [5].  After the brood cells are filled the corridors are filled up with wood pulp [5].

After about three days the eggs will hatch [14,15], and the following development of the larva will take two to three weeks [15]. Then a cocoon is spun in which the larva hibernates [15]. The pupal development will take two to three weeks [15], followed by the emergence of the adult which will live for two to three months [15].

One generation is produced per year, but in long summers two generations are possible [5].

2.3. BEE HOTEL

Sleep and shelter
The males will use the bee hotels as sleeping place [6,9]. Occasionally a fresh female without a nest may do so as well [6,9].

On numerous occasions I have observed how a male that is searches for a suitable spot will hang around the hotels for quite some time, land below an opening, throw a quick glance to inspect the potential spot and take off again. He will land with the antennae directed towards the entrance to sniff it out and crawl head first partially, or entirely inside.
It can take a large part of an hour before the right spot has been found, in which case he will crawl out backwards from the tunnel, turn in front of the entrance and crawl in backwards again so it’s head is pointed towards the entrance when inside.

Agression
From my own observations it turns out that the males looking for a spot on the bee hotel are agressive towards the other bees and wasps on the hotels. When they see an insect they want to scare away they will align themselves in the air with the victim, shoot forward quickly and crash into them. They seem to do this especially with insects near holes in order to scare them away. But they will also attack insects approaching a nest hole in flight. Especially European wool carder bees (Anthidium manicatum) are targeted although these do not seem to be impressed by the harassments.
I have caught a few of these agressive males for identification and they were all E. cavifrons.

2.4. MATING

The males will look for females either actively or passively. In the latter case he will wait in the morning on a sunny leaf on which he put a scent-marking, until a female will pass by [9]. The scent-markings are deposited on the leaf by dragging with their abdomen [9].

On the warmer hours of the day he will actively patrol nearby suitable nest locations for females suitable for mating [9].

Once a female is located he will land on her back and grabs her above the wing base with his middle legs [9]. The front legs are resting over the female’s head with the tarsi along the inner eye edge. As long as the female keeps her wings closed the male will keep his body straightened and his hind legs bend alongside her body so they do not touch the wings [9].

The way he embraces her wings makes it possible for her to still use them, and they may fly up together during mating [9].

When the female opens her wings he will extend his abdomen exposing his genitals, and simultaneously she will bend her body upwards so the genitals meet [9]. Mating may take as long as a few seconds or many minutes [9]. after which the bond of the genitals is broken and she will close her wings again [9].

During mating the males keeps his jaws open so the long palps rest on her stirn and the front legs still positioned in the inner edge of the eyes [9]. During this process the antennae are positioned parallel and downwards with those of the female between them [9]. The shape of Ectemnius male antennae often have rather deep recesses will help to lock them with those of the female [9]. This recesses are species specific [4,5,9], and may have a function during partners selection by the female [9].

Ectemnius cavifrons ♂︎
Ectemnius cavifrons ♂︎

Crabronidae females probably mate only once [15].

2.5. HUNTING

Hunting area

The female has a area in which she will hunt for prey. Throughout it she has a number of lookout positions that are located at the height of the flower horizon or lower looking so she can observe the flower visitors [9]. The outlook positions are used alternately during a period [9].

Like all Ectemnius females she may also actively hunt by flight, during which she will slowly cruise through the herb layer hovering still near flowers [9,15]. When she has spotted a prey she will slowly approach and, in case of a positive identification, explosively accelerate towards the prey and grab it with open front legs and mandibles [15]. This is learned behaviour that she will learn by trial and error [15].

The hunting area may be shared by multiple females [9]. In the rare occasion two females want to use the same outlook position, the new arrival will bump into the present female which will be followed by a staring contents in which the looser will take off [9].

Prey recognition

Probably Ectemnius sees sharp on a distance of about 15 – 20 cm [15].

The female will respond to a potential prey when it enters her field of vision which extends from a few centimetres to about 2 meters [9]. Small insects she will follow by moving her head, larger insects and those on flowers will have her take off to have a closer look [9]. On a distance of about 4 centimetres she will determine if she has found a prey, when positive she will accelerate explosively and throw herself onto the prey and grab it tumbling down to the ground and land somewhere in the foliage [9].
It is not clear whether she will use her sense of smell to recognize prey [9].

Prey handling and transport

The females will keep the caught prey perpendicular underneath her body with her hind and middle legs so the head will extend on one side of her body and the abdomen on the other, the wasp’s sternites are positioned above the thorax of the fly [9]. Grabbing herself with the front legs she will sting the fly in the chest [9].
When the fly is paralysed she will turn it underneath and align it with her abdomen, the abdomen of the fly sticking out underneath her abdomen [9]. During flight the middle legs clamp the neck and the hind legs are used to stabilize the prey [9]. The free front legs are use during landing near the nest entrance after which she will drag the prey into the nest [9].

A hunting sortie will take around 10-15 minutes and when the wasp returns on the nest she will exit for the next sortie in 30s to several minutes [13,14].

3. FOOD PLANTS

Adult wasps feed with nectar. The following plant groups and species are cited in literature as food plants:

Apicaceae
(Umbellifers) [3,4,5]
Angelica [16]
Angelica sylvestris (Wild angelica) [2]

Pastinaca [16]
Pastinaca sativa (Parsnip) [2]

Heracleum [16]
Heracleum sphondylium (Hogweed) [2]
Asteraceae
(Composite family) [3]

Gardenspecies

The garden offers some Umbellifer species but I haven’t observed any Ectemnius species on it yet.

4. PREY RELATIONS

The species ise flies as food for her brood [3,4,5,7].
The following prey groups and species occurring in the Netherlands [1] are cited in literature:

Diptera
(Flies)
Calliphoridae (Blow flies) [4,5,7]
Pollenia
Pollenia rudis [8]

Calliphora
Calliphora vicina [8]

Sarcophagidae (Flesh flies) [7]

Stratiomyiidae (Soldier flies) [7]
Sargus
–  Sargus bipunctatus (Twin-spot centurion) [5]

Syrphidae (Hover flies) [3,4,5]
Episyrphus [10]
Episyrphus balteatus (Marmalade hoverfly) [7,8,14]

Eupeodes
Eupeodes corollae [8,14]
Eupeodes latifasciatus [8,14]
Eupeodes luniger [8]

Helophilus
Helophilus pendulus [14]

Leucozona
Leucozona lucorum [13]

Melanostoma [10]
Melanostoma mellinum [13,14]
Melanostoma scalare [14]

Meliscaeva
Meliscaeva auricollis [14]

Platycheirus
Platycheirus albimanus [13,14]
Platycheirus pellatus [14]
Platycheirus scutatus [13,14]

Rhingia
Rhingia campestris [14]

Scaeva
Scaeve pyrastri [13,14]

Syrphus [10]
Syrphus ribesii [8,14]
Syrphus torvus [8]
Syrphus vitripennis [8,14]

Tabanidae (Horse flies) [4,7]
Chrysops
Chrysops caecutiens [14]
Auchenorrhyncha
(Cicadas)
Cicadellidae
Iassus
Iassus lanio [7,8]

Gardenspecies

The following prey species have been observed in the garden:

Diptera
(Flies)
Syrphidae (Hover flies) [3,4,5]
Episyrphus
Episyrphus balteatus

Eupeodes
Eupeodes corollae
Eupeodes luniger

Melanostoma
Melanostoma scalare

Meliscaeva
Meliscaeva auricollis

5. PARASITIC RELATIONS

The following parasite groups and species occurring in the Netherlands [1] are cited in literature:

Diptera
(Flies)
Anthomyiidae (Muscoidea flies) [5]
Eustalomyia
-Eustalomyia hilaris [5,14,16]

Sarcophagidae (Flesh flies)
Amobia
Amobia signata [17]

Macronychia

Macronychia polyodon [17]
Hymenoptera
(Wasps)
Chalcididae (Chalcid wasps)
Pteromalus [5,7,14]

Chrysididae (Cuckoo wasps)
Chrysis
Chrysis fulgida [7]

Ichneumonidae (Ichneumon wasps)
Perithous
Perithous albicinctus [5,7,14]

Another category of parasites are mites which will not further be investigated here. The males often have one or more clusters of these arthropods cling to their bodies, like this one. The mites are attached to the armor and wings and are present all over his body, especially on the abdomen.

Ectemnius cavifrons ♂︎, infected by mites

6. IDENTIFICATION

Length males: 8 – 12 mm
Length females: 9,5 – 14,5 mm

Genus

The genus Ectemnius can be identified using the following characters:

1.  Front wing with one submarginal cell [3,4,11,12]

Ectemnius cavifrons ♂︎, Ectemnius: front wing with 1 submarginal cel

2. Ocelli usually form an obtuse isosceles triangle [4,11,12]

[JACOBS] specifies: often an acute angle [4].

Ectemnius cavifrons ♂︎, Ectemnius: ocelli form an obtuse triangle (here acute)
Ectemnius cavifrons ♀, Ectemnius: ocelli form an obtuse triangle (here acute)

3. Tergites abdomen smooth with fine punctation, only often slightly stronger on tergite 1 [4,11,12]

Ectemnius cavifrons ♂︎, Ectemnius: tergites smooth with fine punctation

4. Side thorax, metapleuron (M) and often side propodeum (P), with strong transverse wrinkles [3,4,11,12]

Ectemnius cavifrons ♂︎, Ectemnius: side thorax strongly wrinkled

5. Side thorax (mesopleuron) has a short, angular or curved transverse keel in front of middle coxa [4,11,12].

Ectemnius cavifrons ♂︎, Ectemnius: side thorax (mesopleuron) in front middle coxa with short transverse keel
Ectemnius cavifrons ♀︎, Ectemnius: side thorax (mesopleuron) in front middle coxa with short transverse keel

6. Head frontally wider than high [4,11]

Ectemnius cavifrons ♂︎, Ectemnius: head frontally wider than high



Ectemnius cavifrons ♀︎
Ectemnius cavifrons ♀︎
Ectemnius cavifrons ♀︎
Ectemnius cavifrons ♀︎
Ectemnius cavifrons ♀︎, propodeum
Ectemnius cavifrons ♀︎, pygidium


1. Antennae with 12 segments [4,11,12]

Ectemnius cavifrons ♀︎, antennae with 12 segments

2. Abdomen with 6 segments [4,11,12]

Ectemnius cavifrons ♀︎, abdomen with 6 segments

HEAD

1. Ocelli form an isosceles triangle [4,12]

Ectemnius cavifrons ♀, ocelli form an isosceles triangle

2. Distance between hind ocelli (loo) < distance between hind ocellus and eye edge (loe) [12]

Ectemnius cavifrons ♀︎, distance between ocelli smaller than distance between ocelle and eye

3. Vertex at ocelli clearly dented [12]

Ectemnius cavifrons ♀︎, vertex at ocelli dented

1. Antennal segment 3 more than 4x longer than wide [4,11,12]

Ectemnius cavifrons ♀︎, antennal segment 3 is 4x longer than wide

4. Antennal segment 3 is 2x longer than segment 4 [12]

Ectemnius cavifrons ♀︎, antennal segment 3 is 2x longer than segment 4

7. Clypeus golden [4,11,12]

Ectemnius cavifrons ♀︎, clypeus golden

8. Top of the smooth area above antennal base not confined by a transverse keel [4]

Ectemnius cavifrons ♀︎, top smooth antennal zone without keel

9. Inner edge mandible without tooth [11,12]

Ectemnius cavifrons ♀︎, inner edge mandible without tooth in middle

10. Mandible with yellow markings [11]

Ectemnius cavifrons ♀︎, mandibel with yellow markings

11. Clypeus lobe straight ( l1 ) [4,11,12]
12. Clypeus lobe ( l1 ) wider than distance to side tooth ( l2 ) [4,11,12]

Ectemnius cavifrons ♀︎, clypeus lobe (l1) > distance to sidetooth (l2)

THORAX

1. Mesonotum frontally punctated, remainder punctated and wrinkled [11,12]

Ectemnius cavifrons ♀︎, mesonotum front punctated, rest punctated and longitudinal wrinkles

2. Side thorax, mesopleuron, wrinkled [11,12]

Ectemnius cavifrons ♀︎, side thorax (mesopleuron) wrinkled

3. Sides propodeum densely and finely striped, less glossy [11,12]

Ectemnius cavifrons ♀︎, propodeum side densely and finely striped, less glossy

4. Side and dorsal side propodeum not separated by keels [4,11,12]

Ectemnius cavifrons ♀︎, side and dorsal side propodeum not separated by keel

5. Pronotum edges rounded [12]

Ectemnius cavifrons ♀︎, corners pronotum rounded

6. Thorax with yellow markings [12]

Ectemnius cavifrons ♀︎, thorax with yellow markings

7. Underside mesothorax frontally without transverse keel, only developed at the sides [11]

Ectemnius cavifrons ♀︎, front mesothorax ventrally without keel, only developed on the sides

6. Mesonotum and usually tergite 1 with long erect hairs [11]

Ectemnius cavifrons ♀︎, mesonotum and tergite 1 with long erect hairs

ABDOMEN

1. Yellow bands abdomen interrupted in the middle [4,11]

Ectemnius cavifrons ♀︎, yellow bands abdomen in middle interrupted

2. Sternites 5 and 6, or 6 black [4,12], sternite 6 sometimes with yellow spots [5]

Ectemnius cavifrons ♀︎, sternites 5 and 6 black

3. Pygidium black [4,12]
4. Last tergite with channel-shaped, gutter-shaped, pygidium [11]

Ectemnius cavifrons ♀︎, pygidium
Ectemnius cavifrons ♀︎, gutter-shaped pygidium
Ectemnius cavifrons ♀︎, gutter-shaped pygidium

Sternite 7 is also, to a lesser extend, remarkably gutter-shaped, but this is not a character for the species.

Ectemnius cavifrons ♀︎, sternite 7
Ectemnius cavifrons ♀︎, sternite 7



Ectemnius cavifrons ♂︎ (12mm)
Ectemnius cavifrons ♂︎ (12mm)
Ectemnius cavifrons ♂︎ (12mm)
Ectemnius cavifrons ♂︎
Ectemnius cavifrons ♂︎. propodeum


  1. Antenna with 12 segments [4,11,12]
Ectemnius cavifrons ♂︎, antenna male with 12 segments

2. Abdomen with 7 segment [4,11,12]

Ectemnius cavifrons ♂︎, abdomen with 7 segments

HEAD

1. Antennal segment 3 more than 3x longer than wide [4,11,12]

Ectemnius cavifrons ♂︎, antennal segment 3 more than 3x longer (l) than wide (w)

2. Antennal segment 3 with deeply bulged [4,12] and dorsally lightly arched [5,11]

Ectemnius cavifrons ♂︎, antennal segment 3 deeply bulged and dorsally lightly arched

3. Antennal segment 3 with tooth in middle [4,11,12]

Ectemnius cavifrons ♂︎, antennal segment 3 with tooth in middle

4. First tooth antennal segment 3 without hair brisstle [4,11,12]

Ectemnius cavifrons ♂︎, no hair brisstle with bend hairs on first tooth antenna segment 3

5. Antennal segments 4 and 5 strongly cut out [4,11,12]

Ectemnius cavifrons ♂︎, anennal segments 4 and 5 strongly cut out

6. Antennal segment 6 without deformations [4,11,12]

Ectemnius cavifrons ♂︎, antennal segment 6 without deformations

7. Clypeus golden [4,11,12]

Ectemnius cavifrons ♂︎, clypeus golden

8. Inner edge mandible without tooth [11,12]

Ectemnius cavifrons ♂︎, inner edge mandibel without tooth

9. Vertex before ocelli clearly dented accros the whole width [11,12]

Ectemnius cavifrons ♂︎, vertex completely indentated around ocelli
Ectemnius cavifrons ♂︎, vertex completely indentated around ocelli

Top smooth area above antennal base not confined by a transverse keel (not a species character)

Ectemnius cavifrons ♂︎, smooth area above antennal base without transverse carina (not species character)

THORAX

1. Mesonotum punctated and wrinkled [4,11,12]

Ectemnius cavifrons ♂︎, mesonotum punctated and wrinkled

2. Side thorax, mesopleuron, wrinkled [4,11,12]

Ectemnius cavifrons ♂︎, side thorax, mesopleuron, wrinkled

3. Sides propodeum finely striped [12]

Ectemnius cavifrons ♂︎, sides propodeum finely striped

4. Side and dorsal side propodeum not separated by keel [4,11,12]

Ectemnius cavifrons ♂︎, side and dorsal side propodeum not separated with carina

5. Underside mesothorax frontally without transverse keel [11]

Ectemnius cavifrons ♂︎, mesothorax ventral frontally without carina

6. Legs with yellow markings [12]

Ectemnius cavifrons ♂︎, legs with yellow coloring

7. Trochanter front leg without tooth or high keel [4,12]

Ectemnius cavifrons ♂︎, frontal trochanter without tooth or keel

8. Thigh (femur) front leg without tooth [11]

Ectemnius cavifrons ♂︎, frontal femur without tooth

9. Innerside basitarsus middle leg widened before top [11]

Ectemnius cavifrons ♂︎, inside basitarsus middle leg enlarged before tip

10. Front leg tarsal segment 5 strongly widened and rounded [11]

Ectemnius cavifrons ♂︎, middle leg tarsus 5 strongly widened

ABDOMEN

1. Last tergite without pygidium [4,5]

Ectemnius cavifrons ♂︎, tergite 7 wthout pygidium

2. Last tergite with short hairs, edge curves gradually into sides

Ectemnius cavifrons ♂︎, tergite 7 arches gradually to the sides



References

1 Nederlands Soortenregister

2 Waarneming.nl

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 KLEIN, Wim. De graafwespen van de Benelux. Jeugdbondsuitgeverij, Utrecht, 1996, 1-130. + KLEIN, Wim. De graafwespen van de Benelux: supplement. Jeugdbondsuitgeverij, 1999.

5 Koch, F. (2002), 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

6 Breugel, P. van 2014. Gasten van bijenhotels. – EIS Kenniscentrum Insecten en andere ongewervelden & Naturalis Biodiversity Center, Leiden.

7 LELEJ, Arkady (ed.). 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, 2019, 11.2: 13195-13250.

8 BLAND, K. P. An observation of the prey species of the solitary wasp, Ectemnius cavifrons (Hymenoptera: Sphecidae). BRITISH JOURNAL OF ENTOMOLOGY AND NATURAL HISTORY, 2003, 16.1: 9-11.

9 Jacobi, Bernhard. (2001). Beutefang und Paarungsverhalten bei Ectemnius (Clytochrysus) cavifrons (Thomson, 1870) (Hymenoptera, Sphecidae, Crabroninae). 81 - 88.

10 Gabel, Martin & Wolters, Volkmar & Jauker, Frank. (2018). Beobachtungen zum Verproviantierungsverhalten des Wald-Fliegenjägers Ectemnius cavifrons (Thomson, 1870) in einer Nestansammlung auf dem Hoherodskopf (Vogelsbergkreis) (Hymenoptera, Crabronidae).

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 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.

13 PICKARD, R. S. Relative abundance of syrphyd species in a nest of the wasp Ectemnius cavifrons compared with that in the surrounding habitat. Entomophaga, 1975, 20.2: 143-151.

14 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.

15 LOMHOLDT, O. 1975-1976; 1984 (2. Auflage). The Sphecidae (Hymenoptera) of Fennoscandia and Denmark. Fauna Entomologica Scandinavica, 4.1: 2.

16 WOYDAK, Horst. Hymenoptera Aculeata Westfalica Familia: Sphecidae (Grabwespen), 1996, 3-135.

17 POVOLNY, D. The flesh-flies of Central Europe (Insecta, Diptera, Sarcophagidae). Spixiana supplement, 1997, 24: 1-260.

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