1. DISTRIBUTION

Coelioxys elongata ^{[Soortenregister]} occurs at the coast, the higher sandgrounds and in the hills ^{[Peeters et al. 2012]} and is a rare species in the Netherlands ^{[Waarneming.nl]}.

2. BEHAVIOUR

2.1. ACTIVITY

The species is active from May to September ^{[Peeters et al. 2012]}.

2.2. DEVELOPMENT

Coelioxys are broodparasitoids on primarily Megachile species. The Coelioxys species can therefor be found where its hosts nest, ie. in plant stemms or old wood borings ^{[Peeters et al. 2012]}. Since a number of hosts aso will use artificial nest blocks like bee hotels, they can be found on those too.

They produce one generation per year ^{[Peeters et al. 2012]}.

When the female has located the host’s nest it will enter it abdomen first and deposit an egg in the rear wall of the brood cell ^{[Peeters et al. 2012]}.
The first and second instar larvae are tied to the egg shell ^{[Peeters et al. 2012]}. The first instar will develop within twelve hours into the second instar ^{[Peeters et al. 2012]}. The second instar has jaws it can use to kill the host larva. The third instar moves freely through the brood cell and shows predatory behaviour. It will consume the host egg or larva or potential other Coelioxys larvae present in the nest cell ^{[Peeters et al. 2012]}. The third, fourth and fifth instars eat the pollen from the host brood food supply ^{[Peeters et al. 2012]}.

2.3. NECTAR PLANTS

The adult animals can be found on flowers where they drink nectar. Coelioxys bees have a long tongue and visit only flowers in which the nectar lies deep.
C. elongata uses the following nectar plants in my garden (own observations, the gender is shown on the specific flower):

Cabbage family (Brassicaceae)	– Dame’s rocket (Hesperis matronalis), ♂
Rock rose family (Cistaceae)	– Halimium umbellatum, ♀
Sage family (Lamiaceae)	– Oregano (Origanum vulgare), ♂ – Salvia sp., ♀
Legume family (Leguminosae)	– Broad-leaved sweet pea (Lathyrus latifolius), ♀

3. PARASITIC RELATIONS

MEGACHILIDAE are the primary hosts of C. elongata ^{[Peeters et al. 2012],[Nieuwenhuijsen 2010]}.

The following hosts mentioned in the literature can be found in the Netherlands:

Bees (MEGACHILIDAE)

– M. centuncularis [Peeters et al. 2012],[Nieuwenhuijsen 2010],[Rowson & Pavett 2008] – M. circumcincta [Peeters et al. 2012],[Nieuwenhuijsen 2010] – M. leachella [Peeters et al. 2012],[Nieuwenhuijsen 2010] – M. ligniseca [Peeters et al. 2012],[Nieuwenhuijsen 2010] – M. maritima [Peeters et al. 2012] – M. pyrenaea [Peeters et al. 2012] – M. willighbiella [Peeters et al. 2012],[Nieuwenhuijsen 2010],[Rowson & Pavett 2008]

In the garden the following hosts occur regularly or have been sighted:

Bees (MEGACHILIDAE)

– M. centuncularis [Peeters et al. 2012],[Nieuwenhuijsen 2010],[Rowson & Pavett 2008] – M. leachella [Peeters et al. 2012],[Nieuwenhuijsen 2010] – M. willighbiella [Peeters et al. 2012],[Nieuwenhuijsen 2010],[Rowson & Pavett 2008]

4. IDENTIFICATION

The male as well as the female Coelioxys bees are difficult to separate and some species are only identifiable by the genitals (ie. killing them), which is among others true for the male C. elongata.

♀

1. Coxae frontal legs with thorn ^{[Nieuwenhuijsen 2010]}

2. Tergite 6 never points upwards ^{[Nieuwenhuijsen 2010]}

3. Hairbands tergites 2 and 3 uninterrupted ^{[Nieuwenhuijsen 2010]}

4. Gradulus uninterrupted ^{[Rowson & Pavett 2008]}

5. Hairbands sternites 2 to 4 uninterrupted ^{[Nieuwenhuijsen 2010]}

6. Sternite 2 shiny and densely punctated ^{[Rowson & Pavett 2008]}

This is a secondary character (see discussion with bee expert Albert de Wilde). In this specimen the seternite is not densely punctated and looks more like the character of C. inermis. However the next character on sternite 4 is more important and matches C. elongata.

7. Sternite 4 sideways of the middle dull and densely punctated ^{[Nieuwenhuijsen 2010],[Rowson & Pavett 2008]}

8. Sternite 5 caudally narrowed ^{[Nieuwenhuijsen 2010]}

9. Sternite 5 lightly dented ^{[Nieuwenhuijsen 2010],[Rowson & Pavett 2008]}

This character apparently can also be found on C.inermis (see discussion with bee expert Albert de Wilde), which makes it unreliable.

10. Sternite 6 with two teeth at the sides ^{[Nieuwenhuijsen 2010],5]}

11. Sternite 6 long and narrow, abruptly narrowed at the end into a long tooth ^{[Nieuwenhuijsen 2010]}

12. Upper jaw bend, without a clear angle between the upper and lower halves

♂

Males cannot be separated from C. inermis and C. mandibularis without investigation of the genitals.

1. Coxae frontal legs with thorn ^{[Nieuwenhuijsen 2010]}
2. Tergite 6 with six thorns ^{[Nieuwenhuijsen 2010],5]}
3. Edge sternite 4 complete and rounded, sometimes with a slight indentation ^{[Nieuwenhuijsen 2010]}
4. No tooth between thorns sternite 6 ^{[Nieuwenhuijsen 2010]}
5. Spurs hind leg light brown ^{[Nieuwenhuijsen 2010]}
6. Temples as wide as eye with or narrower, tergite 2 denser punctated at base than on rest ^{[Nieuwenhuijsen 2010]}
7. Genostylus apically somewhat enlarged ^{[Nieuwenhuijsen 2010]}
8. Hairbands tergites 2 to 5 uninterrupted in fresh specimens ^{[Rowson & Pavett 2008]}
9. Hairbands sternites 2 to 4 uninterrupted ^{[Rowson & Pavett 2008]}

 

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Literature

^{Nieuwenhuijsen 2010} Nieuwenhuijsen, H., 2010. Determinatietabel voor de bijen van het genus Coelioxys in Nederland. HymenoVaria, 1(1), 32-35.

^{Peeters et al. 2012} Peeters, T.M.J., H. Nieuwenhuijsen, J. Smit, F. van der Meer, I.P. Raemakers, W.R.B. Heitmans, C. van Achterberg, M. Kwak, A.J. Loonstra, J. de Rond, M. Roos & M. Reemer, 2012. De Nederlands bijen (Hymennoptera: Apidae s.l.). - Natuur van Nederland 11, Naturalis Biodiversity Center & European Invertebrate Survey - Nederland, Leiden.

^{Rowson & Pavett 2008} Rowson, R., & Pavett, M., 2008. A visual guide for the identification of British Coelioxys bees. Privately published, Cardiff, UK.

^{Soortenregister} Nederlands Soortenregister

^{Waarneming.nl} Waarneming.nl

Citation

Krischan, O.R., 2025. Coelioxys elongata. Kerfdier, www.kerfdier.nl. Accessed on 20 April 2025.