Scent Mimicry... the story of the beewolf and the cuckoo wasp

The European beewolf (Philanthus triangulum) hunts worker honey bees (Apis mellifera) almost exclusively as a food source for offspring (Strohm et al, 2008). The female beewolf paralyses the worker bee and stores several of them in an underground nest chamber up to 1m long (Strohm et al, 2008). The beewolf then closes up the nest entrance and creates a side entrance where she enters and creates a chamber for brood where she will store 1-6 of the paralysed bees – on one she will deposit an egg (Strohm et al, 2008). The female beewolf even licks the bees, depositing a secretion from the postpharyngeal glands that prevents fungal growth on the bee before the egg can hatch, ensuring there are provisions for her young (Herzner et al, 2007). The beewolf then closes up the brood chamber carefully and never has any contact with her offspring, but she makes sure to leave the kids a packed lunch (Strohm et al, 2008).

European beewolf (Philanthus triangulum) and paralysed worker  honey bee (Apis mellifera)

The female beewolf leaves little opportunity for her vulnerable young to be predated on as she waits until after she has collected food before depositing an egg, then immediately closes the chamber (Strohm et al, 2008). The biggest threat to the beewolf is brood parasitism, and it is believed the beewolf has adopted behaviours to avoid hunting when the parasite species is most active known as an ‘enemy-free space strategy’ (Polidori et al, 2010).

cuckoo wasp (Hedychrum rutilans) approaches beewolf (Philanthus triangulum) nest

There is a specialised cuckoo wasp (Hedychrum rutilans) that has adapted to parasitise the beewolf by depositing an egg in with the beewolf offspring and provisions, that egg hatches and the larvae eats both the paralysed bees and the beewolf offspring. It is believed the cuckoo wasp adopts a combination of strategies to prevent being detected by the beewolf. The cuckoo wasp remains motionless or runs away when they run into the beewolf in her nest and the cuckoo wasp doesn’t leave much evidence of their deception (Strohm et al, 2008). The most interesting strategy though is that the cuckoo wasp avoids detection when they are confronted by a beewolf inside her nest by producing scents very similar to that of the beewolf and leaves inconspicuous scent marks when they deposit an egg into the paralysed bee – this is believed to be the first known chemical mimicry in a parasite of a solitary wasp (Strohm et al, 2008).

Below is a video showing an interaction between the small parasitic cuckoo wasp and the much larger beewolf.

References:

Strohm,E, Kroiss, J, Herzner,G, Laurien-Kehnen, C, Boland, W, Schreier, P & Schmitt, T 2008, ‘A cuckoo in wolves' clothing? chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae)’, Frontiers in Zoology, vol. 5.

Herzner, G, Schmitt, T, Peschke, K, Hilpert, A & Strohm, E 2007, ‘Food wrapping with the postpharyngeal gland secretion by females of the European beewolf Philanthus triangulum’, Journal of Chemical Ecology, vol. 33, pp. 849–859.

Polidori, C, Bevacqua, S & Andrietti, F 2010, ‘Do digger wasps time their provisioning activity to avoid cuckoo wasps (Hymenoptera: Crabronidae and Chrysididae)?’, Acta Ethol, vol. 13, pp. 11-21.

Image 1: Schmidt, Y 2005, Sphecidae of Europe - Hymenoptera Information System, viewed 28 May 2015, <http://uae.hymis.eu/images001/337_Philanthus_triangulum_Juergen_Schmidt_600x400.jpg>

Image 2: Naturalis Historia 2011, Naturalis Historia, viewed 28 May 2015, <http://www.naturalis-historia.de/bilder/Hedychrum%20rutilans%20f10.JPG>

Video: Bee Wolf Wasp v.s. Cuckoo Wasp - slow motion test Corel Video Studio x5 2012, youtube, viewed 28 May 2015, <https://www.youtube.com/watch?v=M3ApIC9B5I4>