The article “Red Admiral Butterflies at Sap”, written by David Nash ( White Admiral 56 :23), reminded me that sap runs from trees are often cited in the literature as food sources for stag beetles (Hyman and Parsons, 1992). Tippmann (1954) (in: Klausnitzer, 1995) reports that at a 20-30 cm gash on an oak tree, he counted over 60 insects, amongst which were four stag beetles, one male and three females. Klausnitzer (1995) notes that the reproductive behaviour of the stag beetle is initiated by the female seeking a source of sap, especially the sap from damaged oak or beech trees, but also chestnut.

Tree sap runs usually result from wind damage, frost cracks, the action of birds, such as woodpeckers, or lightning strikes. The sap that weeps out contains sugars, which come mainly from the damaged phloem tissue. In the majority of species sucrose is the main sugar present, and it can occur in high concentrations, sometimes reaching 25% weight/volume. The sugar in such exudates offers a valuable source of energy for insects. The sap also contains amino acids and mineral elements  (concentrations of potassium and phosphorus in some species are particularly high), which may benefit these arthropods.

Harvey and Gange (2003) report that “adult (stag) beetles do not need to feed and, although they may feed on rotting fruit and sap runs from trees it does little to extend their life span”.

Only a few observations of stag beetles at sap seem to have been recorded. This may be due to its being a relatively rare occurrence, but it is also dependent on the unlikely event of an observer being present   in the right place at the right time.

References

Harvey, D. and Gange, A. (2003). The Private Life of the Stage Beetle ( Lucanus cervus). Bull. Amat. Ent. Soc . 62 (No. 451): 240-244.

Hyman, P.S. and Parsons, M.S. (1992). A review of the scarce and threatened Coleoptera of Great Britain, Part 1. UK Nature Conservation 3. JNCC, Peterborough .

Klausnitzer, B. (1995). Die Hirschkafer. Westharp Wissenschaften, Heidelburg. Tippmann, F. (1954). Neus aus dem Leben des Hirschkafer. Ent. Bl . 50 :175-183.

Colin Hawes, 3 Silver Leys, Bentley, IP9 2BS

© 2004   Suffolk Naturalists' Society