Observations on nestbuilding and prey of the pompilid wasp Anoplius infuscatus (Hymenoptera: Pompilidae)


Published October 2021, Olger R. Krischan

Introduction

An extensive description of the creation of a nest by the pompilid wasp Anoplius infuscatus (Hymenoptera: Pompilidae) [1], a common wasp in the Netherlands, during two independent observations in the Adriaan Tripbos in Sappemeer, Groningen.
In the first observation a digging wasp was encountered with the complete prey lying on a grass poll about 10 cm away from the nest opening.
The second observation started with the arrival of a wasp dragging a complete prey nearby a ready dug nest opening which was excavated, filled, closed and camouflaged during a 2 hour period. During the work the prey was left open and uncovered on the ground at about 14cm distance of the nest.
In both observations the prey was a complete Arctosa leopardus (Araneae: Lycosidae) [1] spider.

Material and Method

Observation area

The observation area is located in the Adriaan Tripbos near Sappemeer in the province Groningen (53.149396, 6.813586, global location in Google maps). It is a constructed forest on sand ground with a small lake in the middle which encloses a piece of land with low plants and shrubs. Inland as well as at the edges open sand planes with low growth can be found.
On about 3-4 meters of the west shore a small flat sandy plane of about 3×3 meters was located between the growth.

Sandy plane with Anoplius nests

This sand plane stuck out between the higher growth surrounding it and the large number of drill holes in the ground (counted: 50, estimated: 100+). At dusk it became clear these holes were occupied by larvae of a tiger beetle, probably Cicindela hybrida.
In both observation the wasps dug their own nests, they did not use an empty Cincindela drill hole.

Drill holes with larva Cincindela sp.

Species determination

I’ve identified the wasp species using the key of [NIEUWENHUIJSEN] [2].

  1. Wasp observation 1: Anoplius infuscatus
  2. Wasp observation 2: Anoplius infuscatus

The prey species have been identified with help of the Waarneming.nl forum, see here:

  1. Spider observation 1: Arctosa leopardus
  2. Spider observation 2: Arctosa leopardus

During the third observation a Arctosa perita spider crossed the area nearby the nest of the second observation.

Observations

On three independent days the sand plane has been observed:

DateWasp present
13-viii-2021Anoplius infuscatus ♀, building nest
15-viii-2021Anoplius infuscatus ♀, building nest
17-viii-2021none
Date and presence nest per observation

All observations have been recorded with two photo camera’s:

  1. Canon 5d Mk IV DSLR with 180mm macro lens – wasp activities
  2. Canon 5d Mk II DSLR with 17-40mm lens – surroundings and overviews

During the photo analysis it turned out the clock of the first camera was trailing 1 hour requiring a correction of 1 hour on the timestamp on the photographs.
For the trip a second hand 5d Mk II DSLR was purchased, used for photographing the surroundings. The clock of this camera turned out to be ahead with 30 minutes.
The in the article mentioned timestamps have been corrected.

Since the first observation duration was short it is summarized in paragraph results.

During the second observation at each change of behaviour of the wasp a new series of photographs have been taken in order to record the behaviour completely, also in time. As a result in most cases there is a small delay between the observation of the change and the start of recording by photographing. The photographic evidence will trail a few seconds in these cases.

The nest was marked with a small stick in the ground for recovery on the third observation day.

On the third observation day there was no wasp present on the plane.

Sequence of behaviour

[ANDRIETTI et al.] [2] define a number of behavioural phases that occur sequentially. This article re-uses these phases and details them further:

  1. Prey capture (PC)
  2. Initial digging (B1)
  3. Definitive digging (B2)
  4. Prey transport and introduction in nest (PT+I)
  5. Oviposition (O)
  6. Nest closing (C)

Result

Individuals

The unique damage on the left forewing tip points to two separate individuals.

Anoplius infuscatus ♀︎, individual 1: front wing damage
Anoplius infuscatus ♀︎, individual 2: front wing damage

First observation

Around 18:50 an Anoplius infuscatus wasp was busy digging a nest opening. During three minutes the wasp was observed until she stopped digging around 18:53 and walked away. I was in company that day and could not continue the observation.

Anoplius infuscatus ♀︎

The lightly coloured sand spheres in the photograph are the excavated materials from the drill holes of the Cincindela beetle larvae. The ochre coloured sand is the material excavated from the wasp’s nest.

Anoplius infuscatus ♀︎
Anoplius infuscatus ♀︎

The photographs show the nest was still shallowly excavated indicating work had started recently. Whether this was part of the initial (B1) or definitive (B2) digging is not possible to say.

The prey

The apparent prey hung in a grass poll at less then 10cm of the nest. During the length of the observation there was no interaction by the wasp with the spider. I assume the spider was visible for the wasp as she was working. No legs had been amputated from the spider.

Anoplius infuscatus ♀, nestlocation and prey
Anoplius infuscatus ♀, prey Arctosa leopardus ♀︎
Anoplius infuscatus ♀, prey Arctosa leopardus ♀︎

Second observation

Two days later the sand plane was visited again. The nest as well as the spider in the grass poll could not be found.

The sand plane was observed from ±18:30 until ±21:00. Around 18:53 about a meter further from the nest of the first observation day another Anoplius infuscatus wasp dragging a prey appeared.

During a period of two hours, up until the wasp retreated into a hiding under a grass poll for the night, the nest building activities have been observed.
Fig. 1 provides a local overview of the nest site and the route followed by the wasp for the transport of the spider toward the nest. The red circles indicate the positions where the spider has been located. The letter P with subscript is used in table 1.

Fig. 1: Anoplius infuscatus ♀, spider transport route

Table 1 provides a schematic overview of the activities with references to Figure 1.

TimeDurationPhaseActivity
PC:
Prey capture
Not observed.
B1:
Nest tunnel digging
Not observed.
18:53:00±00:01:44Wasp dragging with spider.
Spider is dropped (Fig. 1: Pstart) and wasp goes to nest.
18:54:44±00:05:34B2.a:
Brood cell construction
Nest opening cleared. Digging nest.
18:59:34±00:00:58B2.b:
Prey inspection
Digging interrupted.
Wasp returns to spider, relocates it ±1,5cm (Fig. 1: P1).
19:00:32±00:22:14B2.a:
Brood cell construction
Digging continues.
±00:28:46Total duration nest building B2
19:22:46±00:00:43PT+I.a:
Prey transport
Wasp leaves nest.
19:23:29±00:00:08PT+I.a:
Prey transport
Wasp returns at nest.
19:23:37±00:00:13PT+I.b:
Prey transport
Wasp leaves nest, returns to spider.
19:23:50±00:00:10PT+I.b:
Prey transport
Wasp inspects spider, preparing transport, grabs right hind leg.
19:24:00±00:00:17PT+I.b:
Prey transport
Transport of spider, wasp drags spider by right hind leg.
19:24:17±00:00:22PT+I.b:
Prey transport
Transport stops, wasp stings spider (Fig. 1: Psting).
19:24:39±00:00:46PT+I.b:
Prey transport
Transport continued short while. Spider repeatedly gets stuck in growth, during pulling of wasp the spider is turned (Fig. 1: P2)
19:25:25±00:01:09PT+I.c:
Clearing entrance
Wasp arrives at nest nest. Spider located at 3-4 cm distance of the entrance (Fig. 1: P3). Entrance cleared of sand.
19:26:34±00:04:52PT+I.c:
Clearing entrance
Wasp inspects the nest. Additional digging.
19:31:26±00:00:06PT+I.d:
Prey transport
Wasp inspects spider. Spider is relocated a little (Fig. 1: P3) and turned facing the entrance.
19:31:32±00:00:04PT+I.d:
Prey transport
Wasp inspects entrance.
19:31:36±00:00:22PT+I.d:
Prey transport
Wasp grabs right foreleg, transport continues.
19:31:58±00:00:15PT+I.d:
Prey transport
Wasp drops spider at ±1cm of the entrance (Fig. 1: P4), inspects nest inside and outside.
19:32:13±00:00:09PT+I.d:
Prey transport
Wasp grabs right foreleg of spider, transport continues. Spider is positioned face down in the nest opening (Fig. 1: Pfinish).
19:32:22±00:00:42PT+I.d:
Prey transport
Spider is drags by the spinner into the nest. The spider is turned with the abdomen pointing into the nest opening as a result.
±00:10:15PT+ITotal duration prey transport
19:33:04±00:06:41O:
Oviposition
Spider disappeared from view
Oviposition has not been observed
19:39:45±00:07:16C.a:
Filling nest cavity
Wasp appears in opening, start filling the nest cavity.
19:47:01±00:05:18C.b:
Excess sand removal
Nest cavity filled, start removal excess sand.
19:53:43±00:47:50C.c:
Tamping sand
nest cavity
Excess sand removed. Top layer sand removed from nest opening. Start tamping sand in nest opening.
20:41:33±00:07:53C.d:
Camouflaging nest
Tamping finished, start ‘camouflaging’ nest by spreading sand over the surrounding area around nest
20:49:26±00:03:49C.e:
Final inspection
Inspection around the nest
±01:12:06CTotal duration nest closure
20:53:15Nest finished, wasp disappears in hiding for the night
±2 hoursTotal duration until nest finished
Table 1: schematic overview nest building activities

Prey capture (PC)

Catching of the prey has not been observed, the wasp was observed dragging the prey. The spider was located on her back and was dragged by a leg.
The wasp placed the spider on her back in the open on about 14cm distance of the nest (Fig. 1: Pstart).

Initial digging (B1)

The initial digging has not been observed. The wasps had already dug an opening, which she found again after some walking about. She cleared the opening and continued digging, effectively starting phase B2.

Definitive digging (B2)

The wasp dug out material and pushed it up behind her out of the nest tunnel. As she was digging a mount of sand was created on the nest opening. this mount was spread out in a backwards movement around the nest (Fig. B2.1).

Anoplius infuscatus ♀ , clears her nest

After the first prey inspection the intensity and duration of the digging increased. Within ±22 minutes large amounts of sand were pushed from the nest opening from which she now and then appeared, moving backwards to clear the mount.

Anoplius infuscatus ♀, digging

Prey inspection
The wasp interrupted the digging once to inspect the prey, and left the nest opening open and exposed (Fig. B2.2). She found the prey after a short detour and moved it 1 to 2 centimetres (Fig. 1: P1) after which she returned to the nest.
During the second interruption after about 22 minutes of digging she returned to collect the spider. In this case the opening was covered with sand (Fig. B2.3). During the interruption she first made a round around the nest for a duration of about 43 seconds ending at the nest. She did some inspections in and around the nest opening for another 8 second after which she returned with some detours to the spider. The spider was checked and then the transport phase (PT+I) began.

Afb. B2.2: Anoplius infuscatus ♀, nest open as wasp leaves for first prey inspection
Afb. B2.3: Anoplius infuscatus ♀, nest closed as wasp leaves to retrieve prey

Prey transport (PT+I)

The prey was transported by dragging it by the right hind leg using the mandibles.

Anoplius infuscatus ♀, transporting spider

After some centimetres she stopped the transport and stung the spider in her belly (Fig. 1: Psting). I could not observe how many time she stung the spider.

Anoplius infuscatus ♀, stinging spider

Immediately after stinging the transport continued. The path followed crossed an elevation with growth in which the spider repeatedly got stuck. As the wasp pulled the spider eventually turned on her back (Afb. 1: P2).

After arriving at the nest the spider was placed at 2-3 cm of the nest opening (Fig. 1: P3). The nest opening was inspected again. Then the spider was dragged by the right foreleg to about 1 cm of the opening where she was placed. Another nest inspection started. Finally the spider was grabbed by the right foreleg and positioned in the opening face down towards the entrance (Fig. 1: Pfinish). During this activity only the wasp’s head was visible outside the opening.

In the final act the spider was grabbed at the spinner and pulled into the nest, and as a result it turned so the abdomen pointed towards the entrance and entered the nest first. With a few jerks the spider gradually disappeared into the nest in about 30 seconds.

Anoplius infuscatus ♀, introduction spider in nest

Nest closing (C)

Closing of the nest occurred in 5 steps:

  1. filling nest cavity (C.a)
  2. excess sand removal (C.b)
  3. tamping sand nest cavity (C.c)
  4. camouflaging nest (C.d)
  5. final inspection (C.e)
Filling nest cavity (C.a)

After ovipositioning the nest cavity was filled up with the dug up sand collected around the nest opening. The nest resembled a crater at that moment with the nest opening surrounded by a wall of sand. From within the opening the wasp used her legs to shove the sand into the cavity. She worked from the inside outwards resulting in a sand free ring between the opening and the sand wall.

Anoplius infuscatus ♀, filling up nest with sand
Anoplius infuscatus ♀, filling up nest with sand

Every now and then the wasp seemed to hold relatively still while in the nest opening, probably she was tamping the sand with her abdomen, this could not be seen though.
Filling up the nest cavity took approximately 7 minutes.

Anoplius infuscatus ♀, nest filled up with sand
Excess sand removal (C.b)

This phase took some 5 minutes (Table 1).
After the nest cavity was filled up the wasp started spreading the remaining excess sand around the nest opening. She moved the sand in the appropriate direction by moving backwards while sweeping the sand backwards underneath her body with the forelegs.
In the last stage the top layer of the sand in the filled up nest cavity was removed.

Anoplius infuscatus ♀, disperse of excess sand
Anoplius infuscatus ♀, disperse of excess sand
Tamping sand nest cavity (C.c)

A few millimetres of the sand were removed from the filled up nest opening. The wasp now positioned herself above the hole with the abdomen lower into it. In that position she started tamping the sand in the nest opening by pushing her abdomen up and down. Sometimes a more horizontal directed movement was realised by stretching and bending of the abdomen. In all cases the abdomen tip was used as tamper.
The tip was relocated sideways to a new position by moving the abdomen or by repositioning the entire body. During this activity the wasp moved like an irregular clock hand relative to the edge of the nest opening.

Anoplius infuscatus ♀, tamping sand

After tamping she started gnawing pieces of sand from the top layer of the ground around the nest. These pieces were pushed into the nest opening and tamped as well. As a result of the gnawing an arched gutter was created parallel to the edge of the opening. This proved a good marker for me to localise the nest since it became increasingly difficult to spot as the construction continued and the colour became almost indistinguishable from the direct surroundings with the introduction of the top layer sand.

Anoplius infuscatus ♀, gnawing top layer soil
Anoplius infuscatus ♀, tamping nest closure
Afb. C-c.1: Anoplius infuscatus ♀, tamp sand nest plug

The entire tamping phase took 47 minutes (Table 1) which made it the longest phase during the observed nest construction.

Camouflaging (C.d)

In the last step the wasp camouflaged the nest by distributing the excess sand surrounding the nest across a larger area.

Anoplius infuscatus ♀, camouflaging nest
Final inspection (C.e)

After camouflaging the wasp made one final inspection in the direct northbound surrounding and ending it at the nest with which the nest construction came to an end. She left the location in the same direction and disappeared under a grass poll located about 10-15 cm away from the nest location as a hiding place for the night.

End situation

After the nest was finished the nest opening was invisible and difficult to find. The gnawed arched gutter south of the nest opening provided a key character to locating it, indicated by the dotted line in Fig. 2.

Fig. 2: Anoplius infuscatus ♀ end situation after nest building finished

The prey

During the nest construction (B2) the spider was located on the ground, in the open and without cover, at about 14cm of the nest. Originally it was lying on its back. I turned it over to make a photo for later identification. Transported to the nest (PT+I) started in this position, however during transport she was turned over on her back again, see PT+I.

Anoplius infuscatus ♀, prey Arctosa leopardus ♀︎
Anoplius infuscatus ♀, prey Arctosa leopardus ♀︎

Third observation

In the days after the second observation it had rained, removing any marks of the nest and dissolving it into the surroundings. The gnawed gutter resembled no more than some irregularity in the ground making the nest very difficult to find.

Discussion

Prey

The used prey species is part of the known prey group Lycosidae cited in literature [3,4]. The species Arctosa leopardus is not cited under the known prey species in the Netherlands [4].

In both observations no legs were amputated. Amputation is an option for this wasp species and is not applied in all cases [3].

Presence of phase B1

In observation 1 the wasp was found digging. As she interrupted the digging and walked away the observation was stopped and it is unclear whether she was relocating in search of a different nesting site.

Observation 2 started with the wasp dragging a captured prey, and was followed by the digging of the brood cell on a already prepared nest location, which is interpreted by me as the start of phase B2. This deviates from the behaviour described by [ANDRIETTI et al.] [3], although the discussion section of this species in that document refers to one case where a wasp constructed her nest in an earlier prepared nest opening. It is not clear from the text whether that was before or after prey capture. I assume in their phase definition B1 always follows PC.
Digging of initial nests before the definitive nest has not been observed. Possibly this has taken place earlier based on a freshly dug mount of sand covering a hole located 50-100 cm away (estimate on memory) that looked similar to the sand mounts made during this observation. No activity has been observed on the second and third observation days.

Spider positioning

[ANDRIETTI et al.] [3] determine three positioning methods:

  1. the spider is stored in a burrow or hole
  2. the spider is stored on the ground
  3. the spider is stored on an elevation above ground level like grass or small shrub

The observed positioning of the spiders in this article fit these classifications:

observation 1method 3
observation 2method 2
spider positioning in observations

Distance spider to nest

The distance of 10cm in observation 1 cannot be interpreted properly since the observation was prematurely terminated. [ANDRIETTI et al.] [3] report an average distance of 266cm for a a spider lying on grass during phase B1, and 125,83cm during phase B2.

In observation 2 the distance of the spider to the nest measured approximately 14cm which fits the reported average of 15,33cm for the final position before transport into the nest starts [ANDRIETTI et al.] [3].
The distance is about 1/3 of the reported distance of 46,56cm during phase B2 for a prey lying on the ground. A possible explanation could be the earlier excavated nest site as a result of which the wasp already knew where to position the prey approximately. This hypothesis is reinforced by the reported average number of 4,5 visits to the spider during phase B2 [3] in contrast to the here observed single visit during this phase.

The observed distance before introduction into the nest measures about 1cm which fits the reported average of 0,319cm [3].

Spider transport

[ANDRIETTI et al.] [3] establish the spider is transported by:

  1. the cephalothorax-gaster joint (mainly)
  2. the legs (sometimes)
  3. the spinner, during introduction into the nest

Spider transport only has been observed during observation 2 in which it initially was handled by the right hind leg. During transport the spider was turned (Fig. 1: P2), from then on the body part used in transport is not recorded.
Transporting the prey using a leg is the least applied method but it fits the behavioural spectrum.

During introduction of the spider into the nest, transport occurred using the right foreleg up unto the nest opening. For the final introduction into the nest the spinner at the tip of the abdomen was used, resulting in the spider to turn face up. This is conform the expected behaviour [3].

After phase B2 started the spider was relocated once after an interruption of the digging. It was checked and moved ±1,5cm. The remaining transport occurred after the digging was finalized, finishing phase B2 and starting phase PT+I.

Duration nest building

The total time elapsed during nest construction (total duration B2) was 22m14s, which is shorter than the reported average of 42 minutes to 1 hour [3]. As remarked the nest site had already been prepared which may explain the reduced time required to finish construction.

Number of brood cells

In observation 2 one nest cell was built. Although the nest location had been prepared a little, based on the amount of dug out material that covered the nest at the start of phase B2 compared to the amount excavated material during that phase it is clear no cell had been dug out yet.

This is conform reported behaviour [3].

Oviposition

The length ovipositioning, the time measured between introduction of the spider into the nest and the reappearance of the wasp, fits with 6m41s in the reported time of more than 7s [3].

Nest closing

Tamping using the abdomen as well as gnawing of the ground using the mandibles is part of the known behaviour.
[ANDRIETTI et al.] [3] discuss whether or not a centrifugal movement with the abdomen is part of the behaviour. During the here described observation 2 the abdomen could be seen pushing outwards, i.e. backwards (described in ‘Tamping sand nest cavity‘ as “stretching and bending”), which I interpret as a centrifugal motion, see also Fig. C-c.1.

The nest closing observed in observation 2 fits the reported behaviour [3], however the removal of excess sand and the removal of the top layer of the filled nest cavity (C.b) are not mentioned.
Whether the gnawing of surrounding soil top layer really is done with the intent to camouflage the nest needs to be validated with more observations in different soil types.



References

1 Nederlands Soortenregister

2 NIEUWENHUIJSEN, Hans. De spinnendoders van Nederland (Hymenoptera: Pompilidae). Jeugdbondsuitgeverij, 2008.

3 Andrietti, Francesco & Casiraghi, Maurizio & Martinoli, Adriano & Polidori, Carlo & Montresor, Claudio. (2008). Nesting habits of two spider wasps: Anoplius infuscatus and Episyron sp. (Hymenoptera: Pompilidae), with a review of the literature. Annales- Societe Entomologique de France. 44. 93-111. 10.1080/00379271.2008.10697547.

4 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.

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