{"id":817,"date":"2012-03-19T20:53:12","date_gmt":"2012-03-19T20:53:12","guid":{"rendered":"http:\/\/tachinidae.org.uk\/blog\/?page_id=817"},"modified":"2012-04-25T16:08:49","modified_gmt":"2012-04-25T16:08:49","slug":"keys-how-to-spot-a-polideine","status":"publish","type":"page","link":"http:\/\/tachinidae.org.uk\/blog\/tutorials\/keys-how-to-spot-a-polideine\/","title":{"rendered":"Keys: How to spot a polideine"},"content":{"rendered":"

(work in progress)<\/h3>\n

Some species are just trouble right from the start aren’t they? They are usually fairly common species that lack any particularly distinctive features or they are slightly variable. You run them though the key but aren\u2019t all that happy with the result so you try again \u2013 and get to somewhere different. You frown, look slightly vexed, and then try again \u2026 but no matter how you try you are never really happy, so you put it to one side \u201cfor later\u201d. For me this experience is summed up in Lypha dubia<\/em> \u2026 dubia <\/em>by name and dubious by nature! I once sent 5-6 of these common flies over to Peter Tschorsnig, after being completely baffled by them. When I got the identifications back it was a real \u201cfacepalm\u201d moment of epic proportions so I set myself a task of making them easier to key \u2026 such a common fly shouldn\u2019t be that difficult in the keys \u2026 should it?!<\/p>\n

The breakthrough, as is often the way in so many problems, came quite by chance when I was working on a batch of neotropical flies. In the Americas there there is a very diverse tribe called the Polideini and in there I noticed two familiar genera \u2013 Lypha <\/em>and Lydina <\/em>\u2013 both fairly common flies that in Europe were included in a different tribe \u2013 it was like the Polideini didn\u2019t exist here. But in Monty Wood\u2019s neotropical keys this tribe keys out very easily once you locate 2 features that are unused in the British keys by Belshaw \u2013 the metathoracic spiracle<\/em> and the pteropleural bristle<\/em>.<\/p>\n

The metathoracic spiracle is the posterior-most (hind) spiracle on the thorax \u2013 the one that is shielded by the hypopleural bristles and which is located just under the haltere. Here is a photo of a typical spiracle (Exorista rustica<\/em>) – the head is to the left and you can see the flurry, single flap of the spiracle with the hypopleural bristles to the left and the haltere to the right:<\/p>\n

\"\"<\/a>
Exorista rustica spiracle - showing the single flap<\/figcaption><\/figure>\n

The next photos show polideine spiracles, which have small, equally-sized flaps – usually held open:<\/p>\n

\"\"<\/a>
Lypha dubia spiracle - showing the 2 equally sized flaps<\/figcaption><\/figure>\n
\"\"<\/a>
Lydina aenea spiracle - showing the equally sized flaps<\/figcaption><\/figure>\n

The pteropleural bristle, as its name suggests, is just under the base of the wing and if it exists it is usually the largest bristle above the katepisternum \u2013 curving backwards. If you don\u2019t see a huge bristle under the wing, above the katepisternum then your fly probably doesn\u2019t have one.<\/p>\n

[insert photos here of pteropleurals]<\/span><\/p>\n

Now, all you have to check is:<\/p>\n

    \n
  1. Is the pteropleural bristle really long \u2013 long enough to reach back to at least the middle of the biggest calypter?<\/li>\n
  2. Is the metathoracic spiracle made up from 1 rounded flap or from 2 roughly equally-sized flaps (often held open or with a V-shaped gap at the top)?<\/li>\n<\/ol>\n

    If it has both of these features then your specimen is a polideine and sould be either Lypha<\/em> or Lydina<\/em> \u2026 easy!<\/p>\n","protected":false},"excerpt":{"rendered":"

    (work in progress) Some species are just trouble right from the start aren’t they? They are usually fairly common species that lack any particularly distinctive…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":822,"menu_order":0,"comment_status":"open","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-817","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/pages\/817","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/comments?post=817"}],"version-history":[{"count":9,"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/pages\/817\/revisions"}],"predecessor-version":[{"id":819,"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/pages\/817\/revisions\/819"}],"up":[{"embeddable":true,"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/pages\/822"}],"wp:attachment":[{"href":"http:\/\/tachinidae.org.uk\/blog\/wp-json\/wp\/v2\/media?parent=817"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}