This blog provides an informal forum for terrestrial invertebrate watchers to post recent sightings of interesting observations in the southern Vancouver Island region. Please send your sightings by email to Jeremy Tatum ( Be sure to include your name, phone number, the species name (common or scientific) of the invertebrate you saw, location, date, and number of individuals. If you have a photograph you are willing to share, please send it along. Click on the title above for an index of past sightings.The index is updated most days.

January 12

2019 January 12


   Jeremy Tatum writes:  Sher Falls sends a photograph of an insect from Nanaimo in the summer of 2017. While we usually show pictures of recently-photographed invertebrates, we’ll show this one, partly to keep Invert Alert going during the winter months, but also because it is an interesting insect, and to teach me a lesson.


  When I first saw the photograph, I took a quick glance at the narrow, constricted abdomen and confidently declared it to be a hymenopteran of the Family Ichneumonidae.  Beware of people who confidently identify an insect after a brief glance!  It is not a hymenopteran at all – it is a fly!  It is a dipteran of the Family Conopidae.  My book by Colyer and Hammond with the unlikely title of British Flies says that conopids “often bear a striking resemblance to solitary wasps and other hymenoptera”.   Well, I shan’t use that as an excuse, although the insect does do quite a good job of deception. 


  It is a parasitoid of bees, including honey bees and bumble bees.  Apparently the fly attaches itself piggy-back to a bee in flight and lays its egg on the victim.  I quote from  British Flies:  “The larvae are to be found in the front part of the host’s abdomen…  Pupation takes place within the larval skin…  The pupa occupies most of the abdominal cavity of the host…  When the adult conopid emerges, it ruptures the puparium and the enclosing abdominal segments at the same time.”


   We don’t know if the fly is aware of the spider lurking under the flower.


Thick-headed Fly  Physocephala burgessi (Dip.:  Conopidae)  Sher Falls