A Romantic Moment in Insect World

[nonacaremac]

Manfred's spanner insect pic sort of reminded me this pic, which I took a little while back. Insects viewed from above, legs seen through wings etc. So I thought I would post this. I was out checking my veggie patch when I spotted these two. It felt a little voyeuristic but I really liked the colours and the fact that the one on the left (the male I think) has a leg missing. It sort of made the whole nature, survival, reproduction thing just a little bit more real. Amongst all of the trillions and zillions of insects in the world what was the story of this one that resulted in a missing leg. Just another insect so who cares some would say? But for me, everything has a story, its just that most will never be told. Maybe that's part of the reason why we take photographs.

Any and all comments welcome


_P8A3967 by Peter Canton, on Flickr

[DanK]

A very nice capture. I don’t know what these are, except that they must be some type of fly. Perhaps someone can chip in an ID. It’s interesting how much sexual dimorphism there is in this species.


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[Geoff F]

A pair of Nephrotoma craneflies. If this was from the UK I would suspect Nephrotoma flavipalpis.

[DanK]

Hi Peter,

Geoff is the CiC entomologist, but if you aren't familiar with this, I can point out why I knew this was a fly, even though I don't know much about entomology. Flies are the order diptera, which means "two wings". These clearly have only two. This can be tough, however, as it's not always possible to see the four wings on other insects. One definitive mark is the little yellow spherical structures you can see behind the wings. These are called halteres and are thought to have evolved from wings. They are used to stabilize flight. AFAIK, the only other order that has these is very small and not something you're likely to come across.

You can see this clearly in this photo of a fly:



Many flies also have the flat, paddle-shaped antennae you can see here.

Geoff can chime in if I have any of this wrong.

Dan

[Geoff F]

Dan's photo is one of the Empis family. Many flies (and some other insects) don't have common names.

One thing to be wary of, when considering identification, are flies which are mimics of more aggressive insects. For example, some hoverflies are mimics of bees and wasps. They can have longer antennae although still in the three segment form.

There are many flies which have long thin multi segmented antennae so identification can be difficult from angles which don't clearly show the two not four wing arrangement.

And then there are the sawflies which are four winged with various antennae arrangements and some very bee/wasp looking colouration.

Experience is a great aid to identification but it can be difficult when first starting out with entomological identification.

[DanK]

But a sawfly isn't really a fly; it's not in the order diptera. Hence four wings rather than two, and no halteres. If I'm not mistaken, it's in the order hymenoptera, with ants, bees, and wasps.

This is going off topic, but what features are helpful for distinguishing Empis from robber flies? I’ve never found an explanation.

[Geoff F]

For me, Dan, the long tubular mouth is a good pointer to the Empis family.

Robberflies (Asilidae) can have mouth parts which look similar but are much shorter and they usually have some form of long bristle 'beard' above the mouth.

But according to my fly family keys Asilidae key out because of 'Top of head strongly notched either side of a pinnacle on which the ocelli are placed'. Which may be a good feature when viewing under a microscope but it can be hard to see in a photo of a live fly.

Empis separate from many similar flies by wing vein R4+5 being forked (into veins R4 and R5) but the Asilidae veins also fork in a rather similar way.

So it is really just a matter of general appearance and if you can't get a solution by going in one direction it is worth trying the other alternative.

[DanK]

Geoff,

Thanks very much. This is helpful. It seems like the mouth may be the feature easiest to spot in the field.

Dan