Grey-legged Slender Fly
Orange Slender Fly
Orange-legged Slender Fly
Line-legged Slender Fly
Brown-legged Slender Fly
Black-legged Slender Fly
Wasp-mimic Robber Fly I
Wasp-mimic Robber Fly II
Zebra Robber Fly I
Zebra Robber Fly II 


Giant Robber Fly - Phellus olgae

Family Asilidae, Phellinae 

This page contains pictures and information about Giant Robber Flies that we found in the Brisbane area, Queensland, Australia.

Male, body length 45mm  
Giant Robber flies have the wing vein R2+3 open, ending on the wing margin. They have robust and tapering abdomen. Their long wings are broad at the base and tapering gradually to apex. They have wide head and face.
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This is one of the largest fly species with wing-spans up to 75mm. We saw this fly the first time in Daisy Hill Forest during later summer 2005. It was resting on a large tree trunk (River She-oak tree Casuarina cunninghamiana). We noticed the fly by its large compound eyes and golden hairs on its face. It flied fast in short distance with loud buzzing sound.
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The Giant Robber Fly has a dark brown to dark blue body, a pair of golden brown wings, black long and strong legs with short dense golden yellow hairs. We believed the fly in above photos was a male. The flies in those photos below were females, with smaller body size (length 40mm).
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Laying eggs on She-oak pine tree trunk

On a Dec 2007 afternoon we saw a Giant Robber Fly in Karawatha Forest.  We were looking for Variable Jewel Beetle in a She-oak tree area. The Giant Robber Fly landed on a large She-oak tree trunk just in front of us. The Giant Robber Fly looked the same as the one above, except a bit smaller. The abdomen was dark blue in colour and less hairy. This is a female robber fly.
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Female, body length 40mm 
After we took some photos, because we came too closely, the robber fly flied to another She-oak tree a few meter away. Every time we came close, it flied to another tree. After a few minutes chasing, it flied high and disappeared. We went back to where we first met the robber fly, it had already returned there. There were quite a number of large She-oak trees in the area. However, the robber fly only interested on that particular tree. It might sensed something special on that tree.
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The robber fly touched the tree trunk by its abdomen tip and inserting something under the bark. We believed it was laying eggs and inserting them under barks. Its did not check or select the locations for laying eggs on the tree trunk, it just chose the location randomly. It took 10-20 seconds at one spot then flied to another position, same tree, for another 10-20 seconds. 
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We checked the reference materials and did not find much information about robber fly eggs and larvae. In general robber fly larvae live in soil or rotting wood, often regarded them as predacious or parasitic. This Giant Robber Fly found always near the She-oak pine tree could be a hint to be followed. 

Always found on She-oak pine tree trunk

After we learnt that Giant Robber Fly always found on large She-oak tree trunk, they became not too difficult to be found. 
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On Jan 2008 in the same area, we found another Giant Robber Fly. This is also a female. 
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We have the information of another giant robber fly, the Giant Yellow Robber Fly.

Giant Robber Fly Pupal Skin

We found this pupal skin when we were looking for Variable Jewel Beetle. It was on the soil next to a She-oak pine tree, covered by very thick layer of fallen dry She-oak pine leaves. It was strongly armed with spines and hooks. There was the large four points hook at the end tip. 
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Pupal skin length 35mm 
The pupal skin should be a fly pupa and even looked like a robber fly pupa. Because of its size and where it was found, we believed it is the pupal skin of this Giant Robber Fly.

1. Robber Fly - Friends of Chiltern Park Newsletter February 2002.
2. Phellus olgae Paramonov - ACIN, Australian Insect Common Names, CSIRO, 2005.
3. Insects of Australia and New Zealand - R. J. Tillyard, Angus & Robertson, Ltd, Sydney, 1926, p363 (Phellus glaucus).
4. teneral adult next to pupal skin - Whitney Cranshaw, Colorado State University, United States, 2006.
5. Insects of Australia, CSIRO, Division of Entomology, Melbourne University Press, 2nd Edition 1991, p 729, Fig.39.11B. 
6. Robber flies of the world. The genera of the family Asilidae - Hull, F.M. 1962, U. S. National Museum Bulletin 224. (Pts. 1 & 2). U. S. Govt. Printing Office.  

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Last updated: October 23, 2012.