Oil Beetle triungulin larvae

The triungulin larvae of the five currently known species of Meloe in Britain can be identified as follows:

Violet Oil Beetle Meloe violaceus 2 – 2.5 mm long and black in colour (nb a yellow form has been recorded in the past in south-east England). There are two pairs of caudal setae (stiff hairs) at the end of the abdomen. The longest pair are more than half the length of the abdomen. The eggs of this species overwinter and the triungulins appear early in the year at the same time as the next generation of adults. Triungulins can be found from March to June on a wide variety of flowers including lesser celandine and dandelion. They often occur in large numbers and are clearly visible when sitting on yellow flowers.

Black Oil Beetle Meloe proscarabaeus about 1.5 mm long and yellow in colour. There are two pairs of caudal setae at the end of the abdomen. The longest pair are more than half the length of the abdomen. The eggs of this species hatch a few weeks after they are laid. Triungulins can be found from May to July on a wide variety of flowers including thrift and buttercups. Occasionally clumps of newly emerged larvae are found on low vegetation. They occur in small groups and can be difficult to see. Close searching of flowers with the aid of a magnifying glass is an effective way to find them.

Rugged Oil Beetle Meloe rugosus about 0.5 mm long and yellow in colour with a dark brown head and prothorax. There is one pair of caudal setae which are less than half the length of the abdomen. The eggs of this species are laid from October to April. Triungulins can be found from April to July on a wide variety of flowers.

Short-necked Oil Beetle Meloe brevicollis about 0.5 mm long and brown in colour. There is one pair of caudal setae which are less than half the length of the abdomen). The eggs of this species hatch a few weeks after they are laid. Triungulins can be found from June to July on a variety of flowers including hawkbit.

Mediterranean Oil Beetle Meloe mediterraneus about 0.8 mm long and reddish-yellow in colour. There is one pair of caudal setae which are less than half the length of the abdomen. The eggs of this species are laid from October to April. Triungulins can be found in June and July on a wide variety of flowers including thrift and kidney vetch. They occur singly or in small groups and are very difficult to see. Close searching of flowers with the aid of a magnifying glass is the most effective way to find them.

All triunglins are extremely active in warm conditions if a flower is touched lightly they will usually start moving about rapidly.

Meloe triungulins
Meloe violaceus triungulins
Meloe proscarabaeus triungulins
Meloe rugosus triungulins
Meloe brevicollis triungulins
Meloe mediterraneus