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Aphididae : Calaphidinae : Panaphidini : Monellia
 

 

Genus Monellia

Monellia aphids

On this page: Monellia caryella

Monellia [Panaphidini]

Monellia are rather small yellowish aphids, with all viviparae winged. These alatae have a broad body, depressed from the cylindrical cross-section usually found in aphids. The antennal tubercles are slight, but there are two pair of conspicuous tubercles, one directed forward in front of antenna, and one directed backward and sideward. The antennae are about three-fourths as long as body, with oblong-oval secondary rhinaria on segment III. The part of antennal segment III bearing secondary rhinaria is swollen. The prothorax is broad and flat, and the prescutum and scutum of the mesothorax are thoroughly pockmarked. The wings, held horizontal at rest, are symmetrical, tending to bend outward on the coastal margin. The adomen has large rough marginal extensions on segments I, II & III. The siphunculi are hemispherical, as large as the ocular tubercle, opening somewhat anteriorly, and with one curved hair on the posterior edge. All hairs, head to cauda, are pointed. The legs have the fore coxae greatly enlarged. The cauda is knobbed, and the anal plate is bilobed with numerous hairs. Monellia resemble Monelliopsis species, but Quednau (2003) considered them closer to lime tree feeding groups such as Eucallipterus and Tillaphis.

There are only four species in the genus Monellia, all feeding on various species of hickory Carya. Monellia species are all native to North America, but Monellia caryella has been introduced as a pecan pest to South America, southern Europe and the Middle East.

 

Monellia caryella (Blackmargined pecan aphid)

All adult viviparae of Monellia caryella are alate. These alatae are pale lemon-yellow to greenish yellow and hold their wings flat over the back of the body (cf. Monelliopsis species, such as Monelliopsis pecanis, which hold their wings tent-like over the body). The black markings of Monellia caryella are seasonally variable. In spring and early summer they have few black markings (see first picture below for possible spring form). From mid-summer onwards (see second picture below) the most noticeable feature is a broad brown-black band along the anterior margin of the forewing, as well as a continuous broad black band running around the front and sides of the head and down sides of the abdomen as far as abdominal tergite 3 (cf. Monellia microsetosa, which lacks the band on the sides of the abdomen). Autumn forms of Monellia caryella (see third picture below) may also have dark bars across some or all abdominal segments. There are no intense yellow/orange spots visible on the body of the live insect (cf. Monellia microsetosa, which has 2-3 pairs of spots of intense yellow/orange pigment, especially on tergites I-II and V-VI).

First image above copyright Ilona; Second image copyright M.J. Hatfield; Third image copyright Louis Tedders;
All under a Creative Commons Attribution 3.0 License.

The antennae of Monellia caryella are banded, and the part of antennal segment III bearing secondary rhinaria is conspicuously swollen (cf. Monelliopsis pecanis, which has that part only slightly swollen). The spinal hairs on abdominal tergites I-IV are all short and fine (cf. Monellia medina, which has at least some of the spinal hairs quite long). The siphunculi are small, pale and tuberculate (cf Melanocallis caryaefoliae, which has truncate black siphunculi). The body length of alatae is 0.9-2.2 mm. Immatures of Monellia caryella (see first picture below) are pale greenish-yellow with paired dusky spinal and marginal rows of tubercles bearing long capitate hairs.

Blackmargined pecan aphids live and feed on the leaves of hickory (Carya) spp., especially pecan (Carya illinoiensis) and bitternut hickory (Carya cordiformis). Adults and fourth instar immatures feed on the main leaf veins (see second picture above), with the younger instars feeding on the minor veins. Sexuales occur from mid-October to early December. Monellia caryella is widespread in the USA and in Ontario, Canada, and has been introduced into most pecan growing areas including Spain, Israel, Greece, Turkey and Argentina. It is generally regarded as a serious pest of pecan. Intensive spraying in the United States resulted in the development of resistant strains, and nowadays integrated control is more common.

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Acknowledgements

We have made provisional 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 sp 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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References

  • Blackman, R.L. & Eastop, V.F. (2006). Aphids on the world's herbaceous plants and shrubs. Vols 1 and 2. John Wiley & Sons.

  • Quednau, F.W. (2003). Atlas of the Drepanosiphine aphids of the world. Part ii: Panaphidini: Panaphidina. Memoirs of the American Entomological Institute 72, 1-301. Book review