One of three Coelioxys species with similar tips to the female's sternite 6 (two sharp teeth on either side near apex).

Females are more easily determined than males and can be separated from female C. mandibularis by the shape of the mandibles; from C. elongata by the shiny, punctate sternite 4 which contrasts strongly with the duller sternite 5 (sternite 4 dull, shagreened and mostly impunctate in elongata). The apex of tergite 5 is bluntly pointed (a shallow notch is present in elongata).  

Males of these three species are challenging and any records would need to be confirmed by a national expert for confirmation.

Most solitary bees and wasps are difficult to identify, and can rarely be identified from photos taken in the field.  All red-rated records should include a photo or set of photos of the specimen, illustrating the key characters taken from a standard key, which should also be referenced (e.g. ‘Falk, 2015’).  The full set of key characters are generally not visible in field photos and photos are rarely sharp enough. To aid in the verification of your records, please include face shot, side, top and wings.  The notes should state whether male or female, and explain how the specimen met the key characters.  Although NS may not be able to identify the species even if these reference photos are provided, the photos will be stored with the record and may allow it be identified in future.   Alternatively, NS will accept records identified by a recognised local or national expert, or that have been identified via BWARS’ Facebook https://www.facebook.com/profile.php?id=100065021433202 .  If you have obtained this advice, please note the name of the person/organisation identifying the record in the ‘determiner’ field (e.g. ‘Stuart Roberts, BWARS Facebook’) rather than just a comment of ‘BWARS Facebook’.

Found in the same habitats as its hosts, though it appears to be found more frequently in dune systems at coastal sites than at inland locations.

It is on the wing from late June or July to August.

This species is a cleptoparasite of Megachile maritima and M. centuncularis. The females of all but one British species of Coelioxys have a pointed sixth tergite and fifth sternite which is apparently used to cut open the cell wall or cap of the host species. An egg is laid in this slit with at least one third protruding through into the cell or laid directly onto the host egg. There is currently no data to suggest which method C. inermis employs. Generally, Coelioxys larvae kill, and in some species eat, the host egg immediately on hatching. Pupation occurs within a cocoon spun within the host cell where the larva overwinters as a pre-pupa, prior to final pupation, presumably in spring of the following year.

Largely a southern species, appearing to favour the south-east of England but also the south coast of Wales. There are sporadic records from the south-west northwards to Cumberland and Yorkshire.

Status in Leicestershire and Rutland not known.