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Aphididae : Aphidinae : Macrosiphini : Pleotrichophorus
 

 

Genus Pleotrichophorus

Bristly anthemid aphids

On this page: Pleotrichophorus chrysanthemi glandulosus gnaphalodes oestlundi quadritrichus stroudi

Pleotrichophorus [Macrosiphini]

Pleotrichophorus are medium-sized pale spindle-shaped aphids. They have fairly low antennal tubercles and a moderately developed median frontal tubercle. The antennae have a very long terminal process, and both apterae and alatae have secondary rhinaria on some of the antennal segments. The terminal (fused 4th and 5th) rostral segment is pointed or stiletto-shaped. The apterae have a membranous dorsum, with numerous thick, rather short fan-shaped or capitate hairs in 2-3 irregular transverse rows on each segment. The siphunculi are long and slender, sometimes slightly expanded at the apex with a small flange, and the cauda is finger-shaped, tongue shaped or triangular.

Alates have dark intersegmental sclerites and dusky marginal sclerites. The veins on the forewings are conspicuously dark-bordered.

There are about 60 species of Pleotrichophorus worldwide, mostly in the Americas, but with seven in Europe. They do not host alternate, but remain all year on members of the Asteraceae, especially those in the tribe Anthemideae. Pleotrichophorus aphids are not attended by ants.

 

Pleotrichophorus chrysanthemi (Bristly chrysanthemum aphid) Cosmopolitan where chrysanthemums grown

Adult apterae of Pleotrichophorus chrysanthemi (aphid top-right in second picture below, the others are immature) are pale green to yellowish, with longitudinal bands of light wax dusting which give the appearance of darker green median and pleural lines. The apices of their antennae, tibiae and siphunculi are dusky, and the tarsi are dark. The antennae are longer than their body, with a very long terminal process, 5-9 times the length of the base of antennal segment VI (cf. Coloradoa rufomaculata, which has antennae shorter than the body). The head has antennal tubercles, and a moderately-developed median frontal tubercle, all bearing capitate hairs. The rostrum reaches to just past the second coxae, and the apical segment is narrow and acuminate (=tapers to a point). The abdomen has a membranous dorsum bearing many strongly capitate hairs (cf. Coloradoa rufomaculata, which has fan-shaped dorsal hairs). The siphunculi are pale with a dusky apex, very thin, about as long as antennal segment IV, and with no polygonal reticulation (cf. Macrosiphiniella sanborni, which has a zone of polygonal reticulation on the siphunculi). The cauda is pale, rather long and thick, with 3 hairs. The anal plate is slightly darkened, rounded, with a few long hairs. The body length of adult apterae is 1.8-2.4 mm. Immatures (most aphids in pictures below) are very similar to the adult, but have a triangular rather than elongate cauda.

Images above by permission, copyright Sunil Joshi & Poorani, J. Aphids of Karnataka (accessed 12/2/20).

The alate viviparous female (not pictured) is pale yellowish to pale green, with a brown head and thorax, and paired dusky dorsal intersegmental markings. The antennae have 10-18 secondary rhinaria in a line along the whole length of segment III.

Pleotrichophorus chrysanthemi are monoecious on the undersides of leaves of florists' chrysanthemums (Dendranthema). They are entirely anholocyclic, and no sexual forms have been found. The 'species' is thought to have arisen quite recently as a clone of Pleotrichophorus glandulosus able to feed on Dendranthema. Pleotrichophorus chrysanthemi is found in most parts of the world where chrysanthemums are grown.

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Pleotrichophorus glandulosus (Bristly mugwort aphid) Europe, North America

Adult apterae of Pleotrichophorus glandulosus are yellowish white or greenish, sometimes with a pale green median stripe (see first picture below) (cf. Pleotrichophorus duponti which is dull greyish green with green transverse stripes). The antennal tubercles are fairly low with divergent inner faces. The antennae and legs are mainly pale with only the apex of the fifth antennal segment, the base of the sixth antennal segment, and the tarsi dark. The antennae have a very long terminal process. They have numerous thick, short capitate hairs hairs on the dorsum in 2-3 transverse rows on each segment. The siphunculi are long and slender, cylindrical over most of the length but slightly expanded at the tip with a small flange. The cauda is finger shaped. The body length of the adult Pleotrichophorus glandulosus aptera is 1.4-2.6 mm.

The alate Pleotrichophorus glandulosus (not pictured) has a yellowish abdomen with pale brown marginal sclerites and darker pleural intersegmental sclerites.

The bristly mugwort aphid lives on the undersides of the lower leaves of mugwort (Artemisia vulgaris). It can also be found on other Artemisia species and corn chamomile (Anthemis arvensis). Sexuales are produced in autumn with eggs laid on the leaf undersides. Pleotrichophorus glandulosus is found over most of Europe including Britain, and has been introduced to North America.

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Pleotrichophorus gnaphalodes (Frosted sagebrush aphid) Western USA, Mexico

Adult apterae of Pleotrichophorus gnaphalodes (see pictures below) are pale yellowish green, with a frosted appearance produced by dense capitate hairs. The antennae are mainly pale, but dusky from the apex of segment V. The tips of the rostrum and tibiae, and the entire tarsi are dark. The head has rather well-developed antennal tubercles, and a prominent median frontal tubercle. Antennal segment III bears 1-4 secondary rhinaria. The apical rostral segment (RIV+V) has the distal part of RV is extended as a needle-like, cylindrical tip (cf. Pleotrichophorus parilis on Artemisia, which has RIV+V tapering from base to apex). The dorsal body integument is smooth to faintly striate, with a moderately dense cover of capitate hairs without distinct stems. Siphunculi are pale, sometimes with dusky apices (cf. Pleotrichophorus quadritrichus on Artemisia, which has dark siphunculi, and Pleotrichophorus quadritrichus ssp. pallidus, which has dusky siphunculi); they are cylindrical in shape and 0.8-1.6 times the caudal length. The cauda is stoutly elongate, constricted on the basal quarter and the apex broadly rounded, with 5 hairs. The body length of adult Pleotrichophorus gnaphalodes apterae is 1.4-2.2 mm.

Images above copyright Jesse Rorabaugh under a public domain (CCO) licence.

The alate Pleotrichophorus gnaphalodes (not pictured) has the head and thorax brown and sclerotic, with dark brown antennae. The abdomen is pale, membranous, with dusky or light brown sclerites. The siphunculi, anal plate, cauda and anterior wing margins are dusky. Morphologically the alate is much like the viviparous aptera, differing in having more rhinaria (6-19) on antennal segment III, and the presence of marginal & spinal sclerites and longer hairs.

Pleotrichophorus gnaphalodes is monoecious holocyclic on various western species of sagebrush (Artemisia). It is rather widely distributed, with records in California, Colorado, Kansas, and Oklahoma, USA and in Mexico.

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Pleotrichophorus oestlundi (Frosted rabbitbrush aphid) Western USA

In summer the adult apterae of Pleotrichophorus oestlundi (see first picture below) are bluish green to apple green, with apparent white pruinosity (=frosting) resulting from a dense covering of capitate to fan-shaped hairs. In autumn the aphids acquire a slight reddish cast, later turning reddish to reddish brown. The antennae are pale, with antennal joints between segments III & IV, the tips of segment V, and all of VI dark. Antennal segment III bears 1-4 secondary rhinaria, with the longest hairs on that segment less than 0.33 times the basal diameter of that segment. The antennal terminal process is 4.75-7.5 times the base of segment VI. The apical rostral segment (RIV+V) is rather slender, and is 0.75-1.0 times as long as second hind tarsal segment (HTII). The tergum is slightly sclerotic, densely imbricate, spiculate between hair bases and densely covered with uniformly fan-shaped hairs. The siphunculi are only moderately long, 1.0 to 1.8 times as long as cauda, and pale throughout (cf. Pleotrichophorus stroudi on Ericameria, which has long, thin siphunculi which are dark over at least the distal half; and cf. Pleotrichophorus pycnorhysus, which has dark-tipped siphunculi). The cauda has an acute but rounded apex, with slight basal constriction; it is spiculate, and bears 3 pairs of pointed lateral hairs, and 4-10 flattened or funnel-shaped hairs dorsally (cf. Pleotrichophorus wasatchii, which has 2 pairs of lateral hairs, and a single non-capitate dorsal hair on the cauda).

First image above copyright Jesse Rorabaugh, under a public domain (CCO) licence;
second image copyright Andrew Jensen, under a creative commons licence.

The alate Pleotrichophorus oestlundi (see first picture below) is bluish green. The antennae are pale except for the joints between antennal segments III and IV, IV and V, the apices of V, and all of VI, which are dark. Antennal segment III bears 8-14 secondary rhinaria. The wings have dark prominent wing veins. The abdomen is like that of the aptera, but with 3 pairs of rows of sclerites; the spinal ones are small and oval, the pleurals are larger and transverse, and the marginals oval, larger than spinals.

Pleotrichophorus oestlundi is monoecious holocyclic on rabbitbrush (Chrysothamnus spp. and Ericameria spp.) (see second picture above). Sexual forms (red to brownish red oviparae and alate males) occur in October. The frosted rabbitbrush aphid is one of the commoner species of Pleotrichophorus, and is widely distributed in western USA.

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Pleotrichophorus quadritrichus Dark-tailed sagebrush aphid.htm) Western USA

Adult apterae of Pleotrichophorus quadritrichus are bluish green, appearing grey-green over body. The antennae are longer than the body. The antennae are dark, apart from segments III and the proximal half of IV, which are dusky. Antennal segment III bears 1-2 secondary rhinaria, and the terminal process is 3-4 times as long as the base of segment VI. Hairs on the antennae are very short, less than 0.5 times basal diameter of segment III (cf. Pleotrichophorus heterohirsutus, which has the longest hair as long as or longer than the segment basal diameter). The apical rostral segment (RIV+V) is 1.08-1.30 times the length of the second hind tarsal segment (HTII). The dorsal body integument has a moderately dense cover of funnel- or cone-shaped hairs. Both the siphunculi and cauda are dark, except for subspecies pallidus where they may be dusky or rarely pale (cf. Pleotrichophorus gnapholodes, which has pale siphunculi & cauda). The siphunculi are cylindrical, and sparsely armed with small, blunt spicules; the siphunculi are 0.77-1.57 as long as cauda. The cauda is elongate, with a distinct constriction on the basal 0.25 (cf. Pleotrichophorus pullus, which has no such constriction). The cauda has an acute, but rounded apex, and has 5-6 hairs. The body length of adult Pleotrichophorus quadritrichus apterae is 1.15-1.67 mm.

Images above copyright Andrew Jensen, under a creative common licence.

The alate vivipara of Pleotrichophorus quadritrichus has the head, thorax, antennae, legs, siphunculi and cauda all dark sclerotic. The abdomen is pale, membranous, with light brown spinal, pleural and marginal sclerites. Morphologically the alate is much like the aptera except there are more rhinaria on antennal segment III (2-7), the abdomen has 2 small spinal, 2 pairs of pleural and 2 marginal sclerites, and the dorsal hairs are smaller, sparser and less capitate.

Pleotrichophorus quadritrichus is monoecious holocyclic on several species of sagebrush (Artemisia ssp.) Oviparae and alate males occur in October. It is very active, and tends to run fast when disturbed. The dark-tailed sagebrush aphid is common and widespread in western states of the USA.

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Pleotrichophorus stroudi Stroud's rabbitbrush aphid.htm) Western North America

Judging from the picture below, adult apterae of Pleotrichophorus stroudi are green (not recorded in origial description), with a frosted appearance due to fan-shaped dorsal hairs; the antennae are mainly dark. The antennal terminal process is 6.25-7.00 times the base of antennal segment VI. The head bears uniformly funnel-shaped, or widely expanded, frontal dorsal cephalic hairs (cf. the very similar Pleotrichophorus packi, and Pleotrichophorus sporadicus sp. complex, which have those hairs long, with blunt slightly expanded or pointed apices). The apical rostral segment (RIV+V) is 0.71-0.88 times length of second hind tarsal joint (HTII), with 1 basal, 2 dorsal, and 3 lateral pairs of hairs. Dorsal body hairs are moderately dense and funnel-shaped distally. The siphunculi are dark apart from the basal 0.2 (cf. Pleotrichophorus palmerae and Pleotrichophorus elongatus which have only the apices dusky or dark, and Pleotrichophorus packi ssp. brevis, which has only the distal half dark). The siphunculi are 0.22-0.39 times the body length (cf. Pleotrichophorus oestlundi, whose siphunculi are 0.11-0.21 times the body length). The cauda is dusky, elongate, with a slight basal constriction, and an acute apex; it bears 3-5 hairs on each side, and 4 on the posterodorsal surface. The body length of adult Pleotrichophorus stroudi apterae is 2.0-2.5 mm.

Images above copyright Jesse Rorabaugh under a public domain (CCO) licence.

The alate Pleotrichophorus stroudi (not pictured) has the antennae blackish beyond the base of segment III, with 21 or more secondary rhinaria in a crowded single row on segment III. The abdomen has flat to fan-shaped hairs laterally, and on the dorsum. The siphunculi are dusky to blackish, and the cauda is dusky and without capitate hairs.

Pleotrichophorus stroudi is monoecious holocyclic on rabbitbrush (Ericameria nauseosa & Chrysothamnus viscidiflorus), although the sexuales have yet to be found. Clyde P. Stroud first found the species in 1947 by sweeping the vegetation, mainly comprised of grey rabbitbrush (Ericameria nauseosa), at White Sands National Monument in New Mexico, USA. Stroud's rabbitbrush aphid is found in western America.

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Acknowledgements

Whilst we make every effort to ensure that identifications are correct, we cannot absolutely warranty their accuracy. We have mostly made identifications from high resolution photos of living specimens, along with host plant identity. In the great majority of cases, identifications have been confirmed by microscopic examination of preserved specimens. We have used the keys and species accounts of Blackman & Eastop (1994) and Blackman & Eastop (2006) supplemented with Blackman (1974), Stroyan (1977), Stroyan (1984), Blackman & Eastop (1984), Heie (1980-1995), Dixon & Thieme (2007) and Blackman (2010). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections. For assistance on the terms used for aphid morphology we suggest the figure provided by Blackman & Eastop (2006).

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