Poplar leaf aphid

Appearance

Adult apterae of Chaitophorus populicola are yellow brown to shiny black. Their antennal terminal process is normally longer than the base of antennal segment VI.

The longest hair on antennal segment III is about twice as long as the basal diameter of that segment. The fused apical rostral segment (RIV+V) is 0.15 mm long with 2-6 accessory hairs.

Abdominal tergites II-VII are wholly sclerotised and fused into a dorsal plate. There is no pale median line on the sclerotic pronotum nor on the abdominal segments, but the metanotum and abdominal tergite I-III may be partly or wholly pale.

Abdominal tergites II-VII each have pleural as well as spinal and marginal hairs (cf. Chaitophorus nudus which has no pleural hairs on these tergites). There are no evident spinules or nodules on the dorsum (cf. Chaitophorus nodulosus, which has the abdominal tergum evenly spinulose or nodulose). Part or most of the dorsal hairs on the abdomen are tapered to points, blunt, or with chisel-shaped, often forked apices (cf. Chaitophorus populicola ssp. patchae which has all hairs fine and pointed).

Their legs are dark brown to black. The siphunculi are small pale truncate cylinders. The cauda is rounded without any trace of a constriction. The body length of adult apterae is 2.0-2.5 mm. Immature Chaitophorus populicola are reddish brown or dark brown, with a distinctive pattern of dark and pale areas.

Naming

Chaitophorus populicola Thomas 1878
Periphyllus populicolus
Smoky-winged Poplar Aphid

Distribution

Chaitophorus populicola is distributed throughout most of North America.

Behavior

Does not alternate hosts (found on Populus throughout its life cycle).

It feeds and forms colonies only in association with the apical meristem. Dense colonies may develop on young shoots, developing leaves, and leaf petioles (cf. Chaitophorus nudus, which is only found around the trunks of poplar saplings, and probably on the branches of more mature trees). Feeding by Chaitophorus populicola on young leaves induces part of the leaf to fold over, thus partially enclosing the colony. This species is nearly always attended by ants, which remove their honeydew and protect the aphids from predators.

Reproduction

Overwinters in the egg stage. Reproduces parthenogenically during spring and summer. Winged fertile adults appear in late summer.

Food

Chaitophorus populicola has been recorded on 9 species of Populus (Populus acuminata, Populus angustifolia, Populus balsamifera, Populus deltoides ssp. deltoides, Populus deltoides var. occidentalis, Populus euphratica, Populus fremontii, Populus nigra and Populus tremuloides).

Predators

Adult velvet mites (= red velvet mites, true velvet mites, rain bugs, Trombididiidae) predate a variety of soil organisms - and their larvae are parasitic on various arthropods, including aphids. Three genera (Allothrombium, Podothrombium and Monothrombium), are aphid specialists.

Defense

The poplar leaf aphid Chaitophorus populicola has never been recorded without ant-attendents. The tending is done by many different species including Camponotus herculeanus, Camponotus novaeboracensis, Camponotus pennsylvanicus, Formica argentea, Formica dakotensis, Formica montana, Formica oreas, Formica propinqua, Linepithima humile, Myrmica incompleta and Tapinoma sessile (see Siddiqui et al., 2019 and photos shown here). These ants protect their aphids from natural enemies while collecting carbohydrate-rich honeydew. Carl Barrentine has videos showing the ant Formica oreas tending aphids and protecting the aphids from a potential predator at the Turtle River State Park, North Dakota, USA in June 2012.