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Euthoracaphis [Nipponaphidini]Euthoracaphis apterae are flat, oval, 'scale' aphids. The prosoma consists of fused head, thorax and abdominal segment I. This genus is characterized by the unique division of the prosoma by sutures into a large median and two lateral areas, but most other characteristics reveal a close relationship to Nipponaphis and Thoracaphis. Abdominal segments II-VII are fused, and distinctly separated from prosoma and abdominal segment VIII. Antennae in apterae are short and 3-segmented. In alatae the antennae are 5-segmented, with annular secondary rhinaria. The rostrum is short and stout, with the ultimate rostral segment longer than second hind tarsal segment. In alatae the fore wings have the pterostigma a little dusky, with the vein sometimes distinctly bordered brownish; the media vein is once branched. Hind wings have 2 oblique veins. First tarsal chaetotaxy (=number of hairs) is 3, 3, 2 or 3, 3, 3 (fore, mid, hind). The dorsum of the aptera has scattered sculpture or pustules. Dorsal hairs are long, fine, and either sparse or numerous. Abdominal tergite VIII has 2 or 4 hairs. The siphunculi are small and pore-like. The cauda is constricted at base and distinctly knobbed, with a few hairs, and the anal plate is bilobed. Most Euthoracaphis feed on various members of the laurel family (Lauraceae), especially Cinnamomum spp., Machilus yunnanensis, Sassafras variifolium and California bay (Umbellularia californica). But Euthoracaphis longisetosa from northeast India feeds on Senecio sp. (Asteraceae). Euthoracaphis umbellulariae has been reported to be anholocyclic in California), but life cycles of other species are unknown. All species of this genus occur in subtropical or tropical regions. Euthoracaphis species are found in China, India, Indonesia, Japan and North America. Euthoracaphis umbellulariae (California laurel aphid) Western USA, East AsiaAdult apterae of Euthoracaphis umbellulariae are sedentary, aleyrodiform (=whitefly larva shaped), more pointed posteriorly, otherwise pill-box-shaped, black, and covered with white filamentous wax. The integument of the body is quite hard and rigid, with distinct sutures on the prosoma (=head+thorax) dividing it into a large quadrate central area, plus an anterior and two dorsolateral areas (cf. Thoracaphis spp., which have the dorsal area of prosoma entire, with no sutures). All hairs on the prosoma are fine, the longest of them 40-80 μm long (cf. Euthoracaphis heterotricha, which has two longitudinal spinal rows of long thick hairs, 80-125 μm long, in addition to many long and short fine hairs). The antennae are three-segmented, with a conspicuous round rhinarium near the apex of the middle segment, and a number of short spines at the apex of the third segment. The rostrum is short, and three-segmented. The legs are yellow, and conspicuously prominent for members of the genus. The siphunculi are represented by mere rings or pores. The abdomen is reduced in length, and often less waxed than the rest of the dorsum. The cauda is short and wide, and slightly constricted at its base. The anal plate is deeply bilobed. The apterae do not move after they once settle down, and soon become firmly cemented to the leaf surface, where they secrete considerable quantities of white-cottony wax which completely envelops them.
First image above copyright Justin Paulin, second image copyright CA Clarke, Euthoracaphis umbellulariae alatae (not pictured) are jet black with little or no wax covering, standing out in sharp contrast to wax covered nymphs and adult apterous forms in the same colony. The antennae are five-segmented, with numerous annular secondary rhinaria. The body is widest across the front third of the abdomen, with four marginal tubercles on each side, and with the abdominal segmentation quite clearly defined. The siphunculi are mere thickened rings or pores, hardly distinguishable except in cleared specimens. The cauda is short, much wider than long, and slightly constricted at the base. The anal plate is distinctly bilobed. We suspect the bright red nymphs in the second picture above are free-living early-instar nymphs of Euthoracaphis umbellulariae before they secrete wax and 'cement' themselves to the leaf - but we have been unable to confirm or refute this from any published account. The California laurel aphid was first described by Essig (1932) in California, where it is very common on California Bay laurel (Umbellularia californica), and is also recorded from sassafras (Sassafras albidum) and cinnamon (Cinnamomum spp.). Euthoracaphis umbellulariae live and feed on the leaf undersides. Some years later it was also found on leaves of cinnamon in Japan by Takahashi (1959). It seems likely that the aphid was originally introduced from east Asia into California, and not vice versa, because species in the same and related genera are all Asian, also populations in California are anholocyclic. The life cycle of Euthoracaphis umbellulariae in Japan is unknown but, since many Nipponaphidini form galls on winter hazel (Distylium sp.), Blackman suggested that this is their most likely primary host.
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