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Short Notes on Nature Singapore

14 September 2014 | Braconid Wasp | Ichneumon Wasp |

photo I have continued to keep a close watch on the different occupant on a few dead trunk of Rubber Trees, which were still in the upright position except that there were no longer any leaf on them, on a weekly basis. While the Fungus Beetle larvae seen on 17 August has declined substantially due to the decrease in the mushroom population on the trunk, other visitors had move in.

One of them was an orange-head wasp. While I was screening one of my favourite tree trunks last Saturday, I saw 4 of them congregated at one spot of the trunk. I had been noticing this type of wasp in this park for a while, at first as isolated specimen. Soon I started seeing them on these dead tree trunk. The wasp is totally black in colour except for the head and with a slender body.

On the trunk of another tree, one female wasp had inserted the long pointed extension from its tail, called ovipositor, into the tree trunk. From what I read, the purpose is to deposit its eggs into an unfortunate host, likely a grub (immature lava) of a beetle, which happened to be in the tree trunk. The wasp uses a seemingly sophisticated way of detecting the location of its host in the tree trunk --- by tapping the wood with its antennae and collecting signal based on the vibration of the wood with its legs. You can read this interesting post on this phenomenon by an Ichneumon wasp.

photo photo photo photo

photo The 4 wasps seen without the long ovipositor should be the male wasps. Male Ichneumon wasps are known to be gather around site where female wasps are expected to emerge. The male and female wasps shown above might not be the same species since the orange colouration extends to the entire top portion (thorax) of the body in the female. In addition, I had encountered female that looked the same as the orange-head male wasp (see right picture) but with an ovipositor.

After doing some search, I think the one with orange thorax is not an Ichneumon wasp but probably a Zombrus species from the family Braconidae. As for the one with black thorax, I was not able to get to anything close though I suspected that it is either an Ichneumon wasp or braconid wasp.

Update: 29 August 2015

The wasp with black thorax should be a Crown Wasp (Megischus insularis).

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