Most the current iNaturalist posts under C. to California".which is consistent with current BugGuide and iNaturalist posts, which indicate its presence in British Columbia and Utah as well. tridens on its Systema Diptororum page is "Washington to Idaho, s. tridens from Colorado and New Mexico were likely C. ancorals gives its range as "Arizona to Texas".and Curran(1924) speculated that some records for C. The Systema Dipterorum "Nomenclator" page for C. The specimen herein is from " Guadalupe Canyon, Cochise County" in the far southeastern corner of Arizona, within three miles of the New Mexico border. ancoralis material referred to in the papers of Coquillett, Curran, and Shannon was from New Mexico.much of it (perhaps all?) from the Las Cruces area (like the paratype here). In ancoralis the pollinose markings are typically smaller or more often absent than in tridens.Ħ) Range Considerations: All the C. Also, in tridens the porterior portion of the 4th tergite is more abruptly and widely "depressed" (or "crimped") and there are often two small, black, indented spots on either side of the middle.ĥ) In tridens the 4th tergite usually has a more well-defined pair of pollinose (="wax-like dust") brown-to-yellowish markings in front of the posterior yellow band, each usually in the shape of a rectangle with a quarter-circle removed from the antero-lateral portion. Unfortunately, photos from the field often don't show the face clearly, so this may be of limited use.Ĥ) On the 4th abdominal segment, the medial portion of the posterior yellow band projects forward less in ancoralis and has a more gradually-tapered forward edge towards the sides whereas in tridens the yellow usually projects further and more widely forward and is more abruptly-tapered laterally. So this seems a somewhat ambiguous separating character.though a strongly-defined yellow spot on the pteropleuron is presumably indicative of tridens.ģ) Curran's figures 10 & 11 on Plate II indicate ancoralis has narrower and more linear facial markings. But Coquillett's original description of ancoralis mildly contradicts this, as it states there's a "small on lower part of pteropleura, sometimes very indistinct". "ptp" in this labelled image) while tridens positively has a yellow spot on the pteropleuron. In ancoralis that yellow extends further to the sides and is either uninterrupted medially (as in the photo above, and in Ximo's 3rd paratype photo here) or has a fairly narrow black medial line separating the yellow markings on the hind-edge of the vertex (per Curran's 1924 description of ancoralis).whereas in tridens there are always two separate yellow spots, with the medial black separation wider (sometimes only slightly!), and the yellow spots usually don't to extend quite as far laterally.Ģ) Shannon's 1925 key (shown at bottom of the 1st image of this series) states ancoralis lacks any yellow on the pteropleuron (cf. The separating characters are:ġ) In couplet 4 of Curran's 1924 key he used the yellow markings on the upper-back edge of the head to separate ancoralis and tridens. and also scrutinizing BugGuide and iNat posts for both species.there appear to be various characters that can be used to separate the two species––although due to their subtlety (together with variation) each of the characters can sometimes be difficult to decisively interpret. But after studying the original descriptions in:Ĭoquillett(1902) and tridens are quite similar-looking and can easily be confused.
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