Altica palustris

Altica palustris

Although Duff illustrates the female spermathecae of all the Altica species, his key states that five species (all but longicollis) are only safely separable by genitalic characters. From thereon he only keys males so I'm not sure if that's meant to imply specifically male genitalic characters are needed for a safe ID. In any case, even males are difficult and I have not found it easy to assign the males I've caught.

In 2025 I found nearly 60 Altica at a single site over several weeks, a site that was still in arable production until 2024 but is now being restored to heathland. These were found at light, by suction and by sweeping. They were likely to have been associated with willowherbs (some were certainly swept from willowherbs). Unfortunately 2-3 species can be found on willowherbs so this is of limited use. Of 49 that were retained and dissected only two were males, suggesting that the species concerned is (or are) parthenogenetic. The first male was swept from willowherb and mayweed and the other one came to light. I initially identified them as Altica palustris but after examining more I began to lose certainty. Apart from oleracea which is easy to eliminate, the differences in the outline shape of the median lobe seem quite subtle to me and tricky to call. Duff describes differences in the internal keels, grooves and impressions but the diagrams don't really get across the three-dimensional nature of these leaving me uncertain as to how to interpret them. Photographs of median lobes at other websites are mostly taken uncleared and don't really show the internal features well (if at all), and indeed viewing these on the median lobe before clearing them is also very difficult. To see these characters more clearly I have macerated the aedeagus in potassium hydroxide solution, but I still find it difficult to marry up what I'm seeing with the description and diagrams in Duff.

After having doubts about my provisional ID of palustris, I compared the spermathacae of the 47 females with the diagrams in Duff, and taking both the two males and all 47 females into account, I think it is probably safe to label these all palustris.

Here is the first male.

male Altica palusris showing aedagus, Wendling Beck Environment Project (Norfolk, UK), 9th July 2025

Here is the second male. I didn't get a live photo of this beetle and it had become mouldy before I examined it, so in order to remove the mould I soaked the entire beetle in potassium hydroxide. Therefore the colours in the photo are not exactly as in life.

male Altica palusris showing aedagus, Wendling Beck Environment Project (Norfolk, UK), 19th September 2025

Below are the females. The diagram for palustris spermatheca in Duff is the one that most clearly shows a downward-pointing hook-like projection from the tip of the cornu and also the longest collum (although mine show considerable variation here with most having a longer collum than any of the Altica spermatheca diagrams in Duff).

3x female Altica palusris showing spermathecae, Wendling Beck Environment Project (Norfolk, UK), 11th July 2025

5x female Altica palusris showing spermathecae plus spermathecae of another 13 Altica, Wendling Beck Environment Project (Norfolk, UK), 19th September 2025

6x female Altica palusris showing spermathecae, Wendling Beck Environment Project (Norfolk, UK), 2nd October 2025

5x female Altica palusris showing spermathecae, Wendling Beck Environment Project (Norfolk, UK), 25th August 2025

3x female Altica palusris showing spermathecae plus spermathecae of another 2 Altica, Wendling Beck Environment Project (Norfolk, UK), 26th September 2025