Lachnodius Maskell, 1896

Hardy, Nate B., Beardsley Jr, John W. & Gullan, Penny J., 2019, A revision of Lachnodius Maskell (Hemiptera, Coccomorpha, Eriococcidae), ZooKeys 818, pp. 43-88 : 43

Lachnodius Maskell, 1896

Lachnodius Maskell, 1896: 400. Type species: Dactylopius eucalypti Maskell. Subsequently designated by Fernald 1903.

Pseudopsylla : Froggatt 1921: 6. Type species: Pseudopsylla hirsutus Froggatt, by monotypy and original designation. Synonymy by Beardsley 1982: 31.

Biological notes.

The females of all species of Lachnodius induce galls of varying complexity on the leaves, buds, stems, or main trunk of species of Eucalyptus or Corymbia ( Myrtaceae ) (Figs 1, 2). Galls consist of a pit in swollen plant tissue with insect’s dorsum either exposed or partially concealed. Females remain in their gall after their imaginal molt, and then at maturity, depending on species, either desert their gall and move elsewhere for oviposition, or remain in their gall for reproduction. Males, in the few species for which they are known, induce galls as first-instar nymphs but then, near the end of their second instar, vacate the gall and move to another site to form cocoons in which they complete their development.

Diagnosis of adult females of the genus Lachnodius

Body outline circular to oval. In most species eyes on margin (on venter in L. froggatti , and absent in L. sealakeensis ). Antennae six to seven-segmented. Pair of broad, blister-like frontal lobes between antennae; a series of elongate setae along posterior margin of lobes. Tentorial box usually with anterior aliform extensions. Labium either one-segmented, or composed of two fused segments; proximal segment indicated by a pair of setae on ventral surface; distal segment with one pair of ventral seta, one pair of fleshy apical setae, and one pair of dorsal setae. Legs well developed. Anus ventral, with sclerotic rim having fewer than ten setae (except in L. hirsutus ), base of each seta surrounded by ring of minute pores. Anal lobes absent.

Dorsum. Setae short to minute, ≤ 10 µm long (except up to 25 µm long on L. hirsutus ). Microtubular ducts and one or two size classes of macrotubular ducts present; larger macrotubular ducts sometimes with one seta touching rim of dermal orifice; duct shaft of uniform width or constricted near vestibule; macrotubular ducts with vestibule weakly sclerotic and compressed, i.e., not cup-shaped. Derm membranous, sometimes with enlarged microtrichia, sometimes with concave sclerotic granules. Multilocular pores absent. Dorsum delimited by a marginal with fringe of setae, differentiated from other body setae, with shape flagellate, conical or sagittate; marginal fringe either complete around margin, or with break between thorax and abdomen, or with break between thorax and abdomen + break between meso- and metathorax.

Venter. Sometimes larger than dorsum. Setae flagellate, in transverse rows across each abdominal segment, scattered along submargin, in clusters anterior to each coxa. Microtubular ducts usually absent ( L. eucalypti with scattered microtubular ducts on head); macrotubular ducts similar to those on dorsum. Quinquelocular pores dense around vulva, clusters around each spiracle, scattered along submargin and across each body segment.

Etymology.

Although Maskell (1896) did not explicitly state the meaning of the genus name that he coined, his description included a statement that the female insects were either naked or covered in cottony or mealy or waxy secretion. The name Lachnodius thus must be derived from the masculine Greek noun lachno, meaning woolly hair or down.

Key to species of Lachnodius based on adult females