Brachycaudus napelli

Identification & Distribution

Alatae of Brachycaudus napelli (not pictured) have similar characteristics to the apterae except their antennae are about 0.8 times the body length, and the antennal terminal process is about 5 times the base of antennal segment VI. Alatae bear 17-37 secondary rhinaria on antennal segment III and 0-4 on segment IV.

Brachycaudus napelli mainly feeds on monkshood (Aconitum spp.), forming colonies on the stems, flowers and fruits, and sometimes on the leaves. It is also found on delphinium (Delphinium spp.). Both Aconitum and Delphinium species are normally toxic to animals. The aphid does not host alternate, and sexuales (oviparae and apterous males) develop in the autumn. The crimson-tipped monkshood aphid is found in west and north-west Europe, south to Spain, and has also been recorded from Austria and the Czech Republic.

Biology & Ecology

Colour

Crimson red and black is a widely used combination of colours for warning intentional predators (such as birds) and unintentional predators (such as herbivores) that the prey is distasteful or otherwise nasty. The picture below shows the threatened neotropical frog, Oophaga granulifera, otherwise known as the granular poison frog.

Granular poison frog (Oophaga granulifera), copyright Patrick Gijsbers 21/01/08, under a Creative Commons by-sa 4.0 licence.

The aphid Brachycaudus napelli has adopted a similar 'colour scheme'. An aphid can either be using Batesian mimicry (where the insect is not distasteful, but is mimicking one that is) or Mullerian mimicry (where it is distasteful and using a commonly-used warning colour or pattern).

Image above copyright Renze Borkent, all rights reserved.

Given the highly toxic alkaloids present in the foodplant of Brachycaudus napelli, this seems most likely to be Mullerian mimicry. The aphids sequester toxins from their food plant, and redeploy them against predators. Other examples of this are given by Uroleucon tanaceti, which eat tansy (Tanacetum) which contains thujone, camphor and myrtenol, and Uroleucon solidaginis, which eat golden rod (Solidago) which contains pyrrolizidine alkaloids. Read more about aposematic coloration in aphids.

Other aphids on the same host

• Blackman & Eastop list 12 species of aphid as feeding on monkshood (Aconitum species) worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 5 as occurring in Britain (Show British list).

• Blackman & Eastop list 16 species of aphid as feeding on Delphinium species worldwide, and provide formal identification keys (Show World list). Of those aphid species, Baker (2015) lists 7 as occurring in Britain (Show British list).

Acknowledgements We are extremely grateful to Renze Borkent for providing the pictures of this species and Jochem Kuhnen who gave him our contact. Identification was made by Renze Borkent and by us from high resolution photos of living specimens. We have used the keys and species accounts of Stroyan (1964) and Heie (1980-1995), together with information from Roger Blackman & Victor Eastop in Aphids on Worlds Plants. We fully acknowledge these authors and those listed in the reference sections as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

Useful weblinks

References Stroyan, H.G.L. (1964). A note on two Aconitum aphids from Jugoslasvia. The Entomologist 97(1), 129-130.