A Brief Study of the Very Short Siphunculi Section of the Corpuz-Raros and Cook Key to Species of Pleotrichophorus

Andrew S. Jensen, Olathe, Colorado

December 2024

As I’ve written elsewhere, the 1974 paper reporting on the Ph.D. research of Leonila Alzate Corpuz-Raros that analyzed North American Pleotrichophorus was a fantastic contribution that has stood up well to 50 years of use. That said, there are some troublesome aspects in the key and species accounts. Of particular concern over the years has been the section triplet 9 through couplet 14 (Fig. 1) that deals with species that have very short siphunculi (known as cornicles back then). Over the years I have put tentative names on slides that fall into this section of the key, but a couple recent evaluations of my previous sorting indicated that the 1974 paper is inadequate for separating the species that live on sagebrushes (Artemisia). So, I compile here my analysis as it stands today, based on the roughly 100 samples in my collection (Fig. 2).

The 1974 Key to Species and What They Knew

The section of interest in the key begins with a triplet, a thing I was taught to avoid. But, this one serves us well. It pulls out the target species with very short siphunculi, leading us to couplet 10. Here the key tries to pull out Pleotrichophorus obscuratus Hille Ris Lambers as distinct due to dark colored appendages. Over the years I’ve collected samples that had dark appendages but clearly did not fit the other features in the key nor the species account of P. obscuratus. This couplet and the species accounts for P. obscuratus, therefore, comprise our first stop on this journey.

Hille Ris Lambers (1966) described P. obscuratus based on 6 apterous viviparae, 5 from Berkeley, California in February and 1 from about 200 miles south in Pico Creek, California in August. The hosts were recorded as Artemisia californica and Artemisia sp., respectively. Given the coastal location of Pico Creek, the host of that sample was most likely A. californica. Hille Ris Lambers noted that he was reluctant to describe this species based on so little information but went ahead due to what he saw as its distinctive features.

Let’s dive into what Hille Ris Lambers and Corpuz-Raros & Cook say about and did with this species, beginning with the latter and their key couplet declaration: “Legs, antennae, cornicles, and cauda brown.” Material they studied was limited to 2 paratypes from the Berkeley collection mentioned above, plus 5 apterae from Riverside, California, 20 January 1965, on A. californica. We assume from this key wording that all 7 of these specimens had these appendages dark colored. Referring to Hille Ris Lambers, however, we see him qualify his wording about coloration. For example, in the section covering features of mounted specimens he wrote, “Head, antennae, mesosternal furca, legs, stigmal plates, cauda, subanal plate, especially the subgenital plate, and to some extent siphunculi, more or less pigmented to blackish, the rest colorless (page 605).” The problem here is with the phrase “more or less,” but let’s move on to other examples. With respect to antennae he says, “Antennae variable in pigmentation (page 605).” Later he says, “Legs variably pigmented.” So, Hille Ris Lambers noted variation in pigmentation that was ignored in the 1974 key. It is likely that the 2 specimens Corpuz-Raros & Cook borrowed both had brown appendages and then they assumed that the others Hille Ris lambers described were similar. I suspect they were wrong to make this assumption.

So, the 1974 key has been documented as flawed simply by reading the original description of P. obscuratus. Let’s look at other problems I’ve had with this key couplet, which will set the stage for discussion of our second species.

I have 11 short-siphunculi samples of Pleotrichophorus from Artemisia filifolia in Utah and New Mexico, all of which have brown siphunculi and cauda and some have mostly dusky to brown antennae and legs. These are obviously not P. oscuratus, however, based on the length of the ultimate rostral segment (URS), which Hille Ris Lambers gives as “…about 0.11-0.12 mm, slightly longer than base of last antennal segment or second joint of hind tarsi…” In my specimens from A. filifolia the URS is shorter (usually ~0.09 mm), which is about ¾ the length of the base of the 6^th antennal segment and also a bit shorter than the hind tarsal II. These differences seem substantial in the context of Pleotrichophorus taxonomy, so I am reluctant to determine material from A. filifolia as P. obscuratus.

Of course, the obvious option to consider is whether my specimens from A. filifolia are Pleotrichophorus filifoliae (Palmer). So, let’s look at that question for a moment. The 1974 key suggests that P. filifoliae is entirely pale, while my specimens are almost always partially pigmented. So, what were Palmer (1938) and Corpuz-Raros & Cook looking at? Palmer had 14 apterae all collected on 27 August 1919 near Denver, Colorado. Corpuz-Raros & Cook had 1 slide containing 8 of those paratypes plus 1 aptera from 13 May 1939 in Roggen, Colorado (~50 miles northeast of Denver). So, once again the available material was quite limited back then, a problem that almost always leads to weak keys and poor understanding of species. Another likely weakness of this older material is that it would have been slide mounted without clearing. Such specimens are very hard to study in terms of both pigmentation and morphological features. It is possible that these specimens were pale as reported in the papers, or they might have been pigmented like my samples but such pigmentation was not evident in the available slide mounts. In any event, I’ll come back to my samples and what I think about them later. But for now let’s forge ahead in this key.

Triplet 11 tries to separate the remaining 6 species based on length and shape of the URS, a tricky affair especially in writing (pictures speak many words and all that). But, after a few decades of playing with this genus I have a pretty good sense of what they meant and so the triplet is OK with me. Anyhow, it peels off Pleotrichophorus triangulates Corpuz-Raros & Cook, which I have not seen and is not a subject of this essay. It also peels off two species associated with Achillea. The third option is for the remaining 3 species that feed on Artemisia (note that this option is wrong in saying, “on Artemisia or Achillea;” these 3 species only use Artemisia).

Coming to couplet 13, the key peels off Pleotrichophorus infrequenus (Knowlton and Smith) based on a long URS. I have never identified this species, I think for the simple and obvious reason that none of my samples show such a large URS/hind tarsal II ratio. It appears that P. infrequenus has rarely if ever been identified since the original description. Maybe next time we go through the Salt Lake City area we’ll drive up the type locality, Big Cottonwood Canyon, and have a look.

So now we arrive at the last couplet of interest today, which tries to separate P. filifoliae from Pleotrichophorus brevinectarius (Gillette & Palmer). We already know that Corpuz-Raros & Cook had very few, probably poor specimens of P. filifoliae, but how about P. brevinectarius? Gillette and Palmer (1933) based their description on 41 alate viviparae and 4 apterous viviparae all collected at the same time at Chimney Rock, Colorado on 26 June 1932 on a plant identified as Artemisia longifolia. Corpuz-Raros & Cook had 7 of those alatae and 1 of those apterae plus 7 apterae from a place recorded as “Laramie River” Colorado, 9 August 1933, again recorded on A. longifolia, 1 aptera from White Sulphur Springs, Montana, 11 June 1936, recorded on ‘sage’, and 18 apterae from a site probably erroneously noted as GFK (the initials of George F. Knowlton) unless the meaning was that the collection site was Knowlton’s home, wherever that was on 13 September 1941, recorded from Artemisia vulgaris. There are some concerns with this information. The first is the usual: these are not very many samples. Second, the location noted as ‘Laramie River, Colorado’ does not seem to exist. It is possible that the locality was Fort Collins, since there are streets named after Laramie. This is reasonably likely since Fort Collins was the mother ship of Rocky Mountain aphid research in those days. It is also possible that the collector meant to write Wyoming rather than Colorado since the Laramie River does exist, but it is in Wyoming.  Third, the host plants recorded for three of these samples are problematic. Artemisia longifolia, as it is currently understood, does not occur in the Chimney Rock area nor in the Fort Collins area. Artemisia vulgaris is not known from Colorado at all, but since we don’t have a locality other than ‘GFK’ for specimens recorded from this plant we really can’t say much about them. Ultimately we don’t know what host plant any of these samples were found on, and we only have two samples with localities we can somewhat confidently find.

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Analysis of My Samples

I have sorted my material into three broad categories, possibly reflecting the three species of interest in the 1974 key: P. brevinectarius, P. filifoliae, and P. obscuratus. I’ll cover each in detail below in order of increasing difficulty and complexity.

Pleotrichophorus filifoliae (Palmer)

See Table 1 for the 11 samples I have identified as P. filifoliae. See Figure 3 for an example specimen from the 10/22/2024 sample. My specimens are united by a short URS (~0.09-0.10 mm) with a more or less triangular shape (i.e., with little apical needle-like extension), shorter than HTII and a.s. VIa; cauda and siphunculi brown; ratio a.s. VIb/a.s. VIa = ~4-5; head with about 20-28 dorsofrontal setae; dorsal setae uniformly moderately petiolate; a.s. III always with 1 rhinarium in basal half.

These features fit Palmer (1938) and Corpuz-Raros & Cook (1974) quite well. We note that Palmer mentions the cauda being “dusky” while Corpuz-Raros & Cook call it “slightly dusky”, indicating that this coloration is a matter of interpretation. Palmer mentions that the cauda has 2 dorsoapical setae, while Corpuz-Raros & Cook state there is only 1; my specimens have only 1. How this conflict arose is unclear – it is possible that Palmer misinterpreted what she was seeing (easy to do with uncleared specimens) or based this remark on a specimen that was unusual and that Corpuz-Raros & Cook did not see.

Table 1. Pleotrichophorus filifoliae samples studied, representing 33 apterous viviparae.

State	County	Locality	Host plant	Date
NM	Bernalillo	Albuquerque foothills	Artemisia	9/17/2010
NM	Bernalillo	Albuquerque foothills	Artemisia	9/17/2010
NM	Bernalillo	Hills above Albuquerque	Artemisia filifolia	9/25/2022
NM	Bernalillo	hills above Albuquerque	Artemisia filifolia	10/22/2024
NM	Bernalillo	Hills above Albuquerque	Artemisia filifolia	9/14/2016
NM	Bernalillo	Juan Tabo Canyon	Artemisia filifolia	10/24/2024
NM	Cibola	~22 miles S. of Grants	Artemisia filifolia	5/16/2022
NM	Sandoval	Hills above Albuquerque	Artemisia filifolia	9/30/2023
NM	Sandoval	Rio Rancho	Artemisia filifolia	9/26/2022
NM	Valencia	Flats E. of Belen	Artemisia filifolia	10/3/2012
UT	Garfield	S. Escalante nr. Egypt Trail	Artemisia filifolia	5/10/2012
UT	Kane	Coral Dunes Park	Artemisia filifolia	9/24/2013

In summary, my current conception of this species is one that it fits the morphological features mentioned above and most of what Palmer and Corpuz-Raros & Cook describe, and that it is host-specific on Artemisia filifolia (a.k.a. sand sage). The distribution of the species would therefore likely correspond to the distribution of A. filifolia, which is shown in this map: https://bonap.net/MapGallery/County/Artemisia%20filifolia.png.

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Pleotrichophorus obscuratus(?) Hille Ris Lambers

See Table 2 for data on the 19 samples I am considering to be in this tentative category of P. obscuratus(?). See Figure 4 for a photo of an example specimen. My specimens are remarkably uniform morphologically considering that they were collected from 5 species of sagebrush in 7 different U.S. states. They are united by the heavily pigmented appendages, anal plate, subgenital plate, etc. as described by Hille Ris Lambers and Corpuz-Raros & Cook, with the tip of the cauda usually noticeably paler than the rest; the URS is about 0.10 – 0.13 mm, the a.s. VIa being about 1.4-1.5 times as long; URS and HT II are about equal in length; almost all specimens with 1 rhinarium on each a.s. III, but occasionally there are 2 rhinaria; a.s. VIa is about 0.15-0.18 mm, a.s. VIb about 3-5 times as long; cauda with 1 dorsoapical seta except one specimen with 2; head with about 24-32 dorsofrontal setae.

Some of these features fit Hille Ris Lambers and Corpuz-Raros & Cook, others do not. Matching features include the pigmentation pattern, length of URS, density of dorsal setae, ratio of a.s. VIa to VIb, and setation of the cauda. Features that vary include my specimens having a much longer a.s. VIa (0.15-0.18 mm) than the specimens Hille Ris Lambers had (0.10-0.11 mm; Corpuz-Raros & Cook, unfortunately, do not provide antennal segment measurements of the specimens they had from Riverside). Based on the antennal segment measurements provided by Hille Ris lambers, his specimens had generally shorter antennae than mine. These differences in antennal segments, especially a.s. VIa, might be viewed as significant departures within the context of Pleotrichophorus taxonomy. One possibly mitigating factor, however, is that all but one of the specimens studied by Hille Ris Lambers and Corpuz-Raros & Cook were collected in the winter and near the coast. It is possible that habitat and time of year could have affected antennae of their specimens compared to mine, which were all collected inland, on different host plants, and during the late spring, summer, and early fall.

Table 2. Pleotrichophorus obscuratus(?) samples studied, representing 25 apterous viviparae (ap), 1 alate vivipara (al), 9 oviparae (o), and 4 alate males (am).

State	County	Locality	Host plant	Date	Morph
CA	Lassen	Hwy 299, Big Valley pass	Artemisia arbuscula	10/17/2018	ap,o
CO	Jackson	Cowdrey	Artemisia arbuscula	9/29/2019	ap,o
CO	Montrose	Black Canyon area	Artemisia tridentata – WY sage?	9/5/2021	ap
CO	Saguache	Gunnison N.F., above Pauline Creek	Artemisia tridentata – Mt. sage	10/5/2024	o
ID	Owyhee	~10 mi. E. of Jordan Valley	Artemisia arbuscula	7/8/2018	ap
NV	Elko	Harrison Pass	Artemisia rigida	9/20/2013	al
NV	Eureka	Roberts Creek Mt.	Artemisia arbuscula	7/6/2019	ap,al
OR	Harney	Steens Mt., Riddle Ranch	Artemisia – low sage	9/6/2014	ap,al
OR	Harney	Stinking Water area	Artemisia arbuscula	7/4/2018	ap
OR	Harney	Stinking Water Ridge	Artemisia arbuscula	5/2/2015	ap
OR	Harney	Stinking Water Ridge	Artemisia arbuscula	5/2/2015	ap
OR	Harney	Stinking Water Ridge	Artemisia low sage	5/4/2014	ap
OR	Klamath	Winema N.F., Devil’s Garden	Artemisia arbuscula	10/17/2020	o
OR	Lake	Fremont N.F., Rd. 28, ~ m.p. 70	Artemisia cana	10/14/2017	o,am
OR	Lake	Fremont N.F., Rd. 28, m.p. 78	Artemisia cana	10/11/2018	o,am
OR	Lake	Radio Towers above Lakeview	Artemisia arbuscula	9/30/2020	ap,o
OR	Lake	Radio towers area above Lakeview	Artemisia arbuscula	7/20/2018	ap
OR	Lake	West side of Lakeview valley	Artemisia arbuscula	6/9/2019	ap
UT	Cache	Avon Rd. N. of Eden	Artemisia cf. tridentata	8/22/2012	ap,al
WY	Lincoln	Bridger N.F., Greys River, Broad Canyon	Artemisia tripartita	6/20/2024	ap
WY	Lincoln	Bridger N.F., Labarge Creek, Scaler’s Cabin	Artemisia tripartita	6/22/2024	ap

In summary, I think I am going to stick with the name Pleotrichophorus obscuratus(?) on my samples. I suspect, however, that the populations living on A. californica in coastal California are a different species. This mystery might be resolved by collecting sagebrush aphids from the Oregon border south through California to (or into) Mexico and in all seasons of the year.

Pleotrichophorus brevinectarius(?) (Gillette and Palmer)

This is the final and most complicated of the categories (species?) I’ll be covering in this essay. Effectively what I’ve done is compile all specimens that did not fit P. obscuratus(?) and P. filifoliae, as discussed above, into a single box on my shelf. I’ll cover the taxonomy and challenges associated with this group of 69 slides, which I’ll record in my collection as P. brevinectarius(?). See Table 3 for data on the 61 samples I am considering to be in this tentative category of P. brevinectarius(?). See Figures 5-7 for photos of example specimens.

The key feature that I used to separate this group of samples from P. filifoliae and P. obscuratus(?) is the denser dorsal setae, marked by usually 40 to 60 dorsofrontal setae on the head, and these setae are normally short and broadly expanded. Of course there are exceptions, with some specimens, especially from late summer, with about 30 dorsofrontals that seem a bit longer. The main block of specimens in this box have URS 0.11 to 0.13 mm long, 1-2(3) rhinaria on a.s. III, and a.s. VIb about 3.5 to 6 times a.s. VIa. Cauda setae vary in these specimens from the genus-typical 5 to as many as 10.

I have one set of 17 slides from all over the west that have setae longer and slightly less dense, with about 32 dorsofrontals. These specimens otherwise match very well the other features of this group.

Among all my samples, those collected on Artemisia cana tend to be larger than the others and have extra cauda setae (most specimens with more than 7 setae). On the other hand, I have three slides of specimens collected on Artemisia rigida that are smaller than normal, have URS 0.09-0.10 mm, and 8 or 9 cauda setae.

Once again we are confronted with the possibility that among all these samples are separate species affiliated with one or more of these sagebrush species. Probably sets of features could be compiled, for example, to separate samples from A. cana and A. rigida from all the others. Also possible might be features to separate samples from A. arbuscula. But ultimately, I think it best to lump all these under one name for now.

One sample I faced during this sorting had siphunculi uncomfortably long, about 0.16 mm. Running this through the Corpuz-Raros & Cook key we arrive at Pleotrichophorus spatulavillus (Knowlton & Smith). Small variations in siphunculi seem to be the only feature separating this species from the three I’ve covered above. I have grown skeptical of the stability and taxonomic meaning of siphunculi lengths in Pleotrichophorus. So, one lingering worry I have is that something like S. spatulavillus merely represents P. brevinectarius with unusually long siphunculi. After all, I am choosing to group samples with quite a range of setal densities, why not minor variation in siphunculi?

Much more work will be needed to clarify the taxonomy of this group, i.e. whether there are host-specific species and the meaning of some of the characters I and others have focused on.

Table 3. Pleotrichophorus brevinectarius(?) samples studied, representing 12 fundatrices, 102 apterous viviparae (ap), 3 alate viviparae (al), 12 oviparae (o), and 1 alate male (am).

State	County	Locality	Host plant	Date	Morph
CA	Alpine	Humboldt-Toiyabe N.F., slope above Burnside Lake	Artemisia arbuscula	8/1/2019	ap
CA	Modoc	Modoc N.F. – Warners, Summit Trail	Artemisia arbuscula	7/23/2016	ap
CA	Yolo	Davis	Artemisia cf. filifolia	4/16/2014	ap,al
CO	Montrose	Dry Creek Canyon	Artemisia tridentata – Basin big	7/17/2021	ap
CO	Montrose	NE of Transfer Rd. ~m.p. 8	Artemisia tridentata – Basin big	10/16/2021	ap
ID	Custer	Mt. Borah area, Dry Creek	Artemisia – low sage	8/31/2014	ap
ID	Owyhee	Scenic Byway nr. Deep Creek	Artemisia cf. tridentata	10/9/2011	o
ND	Slope	Little Missouri N.G., Burning Coal Vein	Artemisia cana	5/29/2017	ap
ND	Slope	Little Missouri N.G., Burning Coal Vein	Artemisia cana	5/29/2017	ap
ND	Slope	Little Missouri N.G., Burning Coal Vein	Artemisia tridentata	5/29/2017	ap
NM	Rio Arriba	Carson N. F.	Artemisia	9/22/2010	ap
NM	Rio Arriba	Ghost Ranch	Artemisia sp.	10/2/2012	ap
NV	Washoe	Yellow Rock Canyon	Artemisia tridentata	5/28/2016	ap
OR	Harney	Malheur N.F., Hwy 395 at Rd. 3935	Artemisia tridentata	6/29/2019	al
OR	Harney	Stinking Water area	Artemisia tripartita	7/4/2018	ap
OR	Klamath	Klamath Agency	Artemisia tridentata	8/27/1995
OR	Klamath	Klamath Agency	Artemisia tridentata	8/27/1995
OR	Klamath	Winema N.F., Devil’s Garden	Artemisia tridentata	10/17/2020	o,am
OR	Lake	Augur Creek west of Lakeview Valley	Artemisia tridentata	9/21/2020	ap
OR	Lake	Fish Creek ridge, WSA	Artemisia arbuscula	8/2/2020	ap
OR	Lake	Fremont N.F., Abert Rim	Artemisia arbuscula	6/16/2018	ap
OR	Lake	Fremont N.F., Abert Rim area	Artemisia tridentata	7/18/2019	al
OR	Lake	Fremont N.F., N. Warners, nr. BLM border	Artemisia cana	9/13/2017	ap
OR	Lake	Fremont N.F., Rd. 28 ~m.p. 53	Artemisia arbuscula	6/23/2019	f
OR	Lake	Fremont N.F., Rd. 28 ~m.p. 54	Artemisia arbuscula	6/24/2018	ap
OR	Lake	Fremont N.F., Rd. 4020 m.p. 7	Artemisia arbuscula	5/8/2020	f
OR	Lake	Fremont N.F., Warners at N. BLM border	Artemisia arbuscula	7/3/2020	ap
OR	Lake	Hwy 140 at Harney Co. border	Artemisia arbuscula	5/25/2015	ap
OR	Lake	Hwy 140 at Harney Co. border	Artemisia tridentata	5/25/2015	ap
OR	Lake	Hwy 140 at Harney Co. border	Artemisia tridentata	5/25/2015	ap
OR	Lake	Hwy 140 at Harney Co. border	Artemisia tridentata	5/25/2015	ap
OR	Lake	Lakeview Valley, Thomas Creek area	Artemisia arbuscula	4/7/2016	f
OR	Lake	Moss Spring trail NW of Lakeview	Artemisia tridentata	6/24/2017	ap
OR	Lake	North Warners, Mud creek	Artemisia cana	8/15/2016	ap
OR	Lake	Rabbit Hill N. of Lakeview	Artemisia cana	7/9/2020	ap
OR	Lake	Radio Towers above Lakeview	Artemisia arbuscula	9/30/2020	ap
OR	Lake	Trail in hills above Lakeview	Artemisia arbuscula	4/30/2016	ap
OR	Lake	W. side of Lakeview valley	Artemisia arbuscula	8/18/2020	ap
OR	Lake	W. side of Lakeview Valley	Artemisia tridentata	10/2/2018	ap
OR	Lake	Warner Mts. N. of Hwy 140	Artemisia – Wyoming sage	8/30/2015	ap
OR	Lake	Warner Mts., Dismal Swamp	Artemisia cana	7/3/2016	ap
OR	Lake	Warner Mts., ridge above Dismal Swamp	Artemisia arbuscula	7/3/2016	ap
OR	Lake	West side Lakeview Valley	Artemisia arbuscula	6/9/2017	ap
OR	Lake	West side Lakeview Valley	Artemisia arbuscula	6/10/2017	ap
OR	Lake	West side of Lakeview valley	Artemisia arbuscula	6/14/2018	ap
OR	Lake	West side of Lakeview valley	Artemisia arbuscula	6/9/2019	ap
UT	Garfield	S. Escalante nr. Egypt Trail	Artemisia low shrub	5/10/2012	ap
WA	Grant	Frenchman Hills	Artemisia tridentata	6/19/2018	ap
WA	Grant	Road S & 9 NE	Artemisia tridentata	5/3/2009	ap
WA	Grant	Ruff	Artemisia rigida	5/3/2008	ap
WA	Grant	Ruff	Artemisia rigida	6/23/2021	ap
WA	Grant	Wild Horses viewpoint	Artemisia rigida?	6/9/2011	al
WA	Kittitas	Ryegrass Summit	Artemisia longifolia?	5/19/2008	ap
CO	Gunnison	Blue Mesa Reservoir	Artemisia tridentata – WY sage?	6/18/2022	ap
ID	Owyhee	nr. Flint Creek & Duck Creek	Artemisia – low sage	4/28/2013	al
OR	Lake	Fremont N.F., nr. White King mine	Artemisia cana	10/15/2020	o
OR	Lake	Mesa btwn Augur and Camp Creek	Artemisia tridentata	10/13/2020	o
OR	Lake	Rd. 3780 W. of Lakeview valley	Artemisia tridentata	6/17/2016	ap
OR	Lake	Warner Mts., above Big Valley	Artemisia tridentata	7/2/2016	ap,al
OR	Lake	Winter Rim	Artemisia cana	10/8/2016	ap
CA	Modoc	Modoc N.F., Janes Reservoir	Artemisia – ‘low sage’	4/26/2014	ap
ID	Bingham	Lava fields near Blackfoot	Artemisia tridentata – Basin big	6/27/2022	ap
ID	Idaho	Nez Perce N.F., China Creek	Artemisia	5/26/2013	ap
ID	Owyhee	~10 mi. E. of Jordan Valley	Artemisia arbuscula	7/8/2018	ap
OR	Lake	Camp Creek west of Lakeview valley	Artemisia tridentata	10/2/2020	ap
OR	Lake	Fremont N.F., Cox Peak	Artemisia tridentata	9/26/2020	ap
OR	Lake	Fremont N.F., Warner Mts.	Artemisia cana	5/24/2015	f
OR	Malheur	Tim’s Peak nr. Hwy 20	Artemisia tripartita	10/19/2013	ap,o

Amended Corpuz-Raros & Cook Key, Options 10-14

Below I present the section of the key I’ve discussed here, but improved based on my study of these three species. I have not evaluated here the separation of the two Achillea-feeding species. I think the situation with these species would benefit from a fresh look involving much newer material.

10. Rostrum IV+V short (0.08 mm), not much longer than basal width, tapering abruptly to a sharp point (Figure 126); on Agoseris … P. triangulatus

— Rostrum IV+V short (0.09-0.11 mm), but longer than basal width, tapering gradually to rather blunt apex, sides slightly convex; on Achillea … 11

— Rostrum IV+V as short as 0.09 or as long as 0.14 mm but sides straight, apex sharply pointed or produced as needle; on Artemisia … 12

11. Dorsal setae dense, all widely expanded, funnel- to fan-shaped, df setae mostly 28 or more; cornicles usually more than ¾ caudal length (m=0.80 +/- 0.03, n=35) … P. patonkusellus

— Dorsal setae not noticeably dense, anterior head and posterior abdominal setae more slender, longer-stemmed than posterior df’s and discal body setae; number of df’s usually less than 26; co/ca ratio averaging less than ½ (m=0.43 +/- 0.02, n =60) … P. pseudopatonkus

12. Rostrum IV+V 1 2/3, or more, length of hind tarsal joint 2; on Artemisia tridentata … P. infrequenus

— Rostrum IV+V subequal or not more than 1 1/3 times length of hind tarsal joint 2 … 13

13. Dorsal setae dense, mostly without distinct stems, df’s usually more than 20 pairs; cauda and cornicles pale or only slightly dusky; on various shrubby Artemisia spp. … P. brevinectarius

— Dorsal setae less dense, mostly with distinct stems, df’s usually 16 or fewer pairs; cauda and cornicles (and sometimes legs and other body parts) brown; on various shrubby Artemisia spp. … 14

14. Legs with coxae and most of femora dark brown, concolorous with short basal and apical sections of tibiae, majority of tibiae usually pale; rostrum IV+V usually 0.10 mm or more; on various shrubby Artemisia … P. obscuratus

— Legs with coxae and femora pale to dusky, never as dark brown as apex of tibiae; rostrum IV+V usually 0.09 mm; on Artemisia filifolia … P. filifoliae

References Cited

Corpuz-Raros, L.A., E.F. Cook. 1974. A Revision of North American Capitophorus Van der Goot and Pleotrichophorus Börner (Homoptera: Aphididae). Smithsonian Contribution to Zoology No. 156. 143 pp.

Gillette, C.P, M.A. Palmer. 1933. New Species of Aphids from Colorado. Annals Entomological Society of America 26: 348-367.

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