1886.J 27 



Myiilaspis pomoritm, Bouclie. 



Externally nearly all the forms of Mytilaspis are so very similar, that thoy 

 might be believed to constitute but one species ; but good characters for the separa- 

 tion of species exist in the pattern of the fringe of the last abdominal segment, and 

 more especially in the number and relative position of the groups of the wax- 

 excreting spinnerets on the inferior surface of the same segment. In the European 

 species there are fire groups — one anterior (mesal of Comstock), one on each side 

 lower down (anterior-lateral), and one still lower (posterior-lateral). The number 

 of spinnerets in each group is tolerably constant in a species, but it varies within 

 certain limits, not only in the species, but even in the individual, for it is not always 

 exactly the same in the corresponding lateral group. 



For some years past I have known the scales of a Mytilaspis common on red 

 and white currant bushes, and latterly I have found, but more sparingly, scales on 

 the black currant, always on the two-years'-old shoots, all three agreeing exactly in 

 external appearance and similarly not separable from M. pomorum, the species very 

 abundant on apple trees. Dr. Goethe has examined the black currant form with 

 reference to the formula of the spinnerets, and finds that they agree with the form 

 on the apple, but he gives the number of spinnerets in the respective groups as 

 10, 18, 16, whereas Signoret gives them {for pomorum) as IV, 10, 14. This difference, 

 however, is not of importance in a specific sense, for I find that, while the scales on 

 the apple and black currant are identical as regards the fringe, the spinnerets in both 

 vary in number in the respective groups, thus, 8 — 13 anterior, 14 — 21 ant. lat., 

 9— 14 post, lat.* Comstock (Report, 1880) gives the numbers as 11—17, 16—21, 

 16 — 21 in the respective groups. Maskell (Trans. N. Z. Inst., xi, 194) gives the 

 numbers, as shown by scales from apple, plum and lilac, as 17 — 20, 17—19, 14 — 17 

 respectively. There can be no doubt that Goethe's species is M. pomornm, Bouche, 

 but he erroneously calls it M. conchiformis, Gmelin. [I may here mention inci- 

 dentally that I find the Mytilasjiis on the dogwood {Cornus) and plum trees to be 

 identical with the species on the apple (J/, pomorum) as to abdominal fringe and 

 spinnerets ; Bouclic had stated they were the same species, but I apprehend without 

 microscopic test.] 



Mytilaspis linearis, Geoff r., Modeer. 



Gmelin (Syst. Nat., 13 ed., p. 2221, No. 37, 1788) describes Coccus conchiformis 

 in these words, "Habitat in ulmo, angustus, fuscus." 



Signoret adopts the name for a species of Mytilaspis living on the elm, which 

 he finds differs essentially from il/. pcuHorinw, Bouche, inasmuch as the spinnerets 

 are 6 — 7, 8 — 9, and 5 — 6, in the respective groups. lie admits, however, that at 

 first he had been misled by Curtis in employing the r.ame conchiformis for the apple 

 feeder. 



Reaumur expressly states that his figure t. 5, fig. 7 (Gallinsecte en forme de 

 coqullle) represents an elm-feeder, and the figure is cited by Gmelin; but he also 

 gives as a synonym of his conchiformis, Coccus arhorum linearis, Modeer, " Act. 

 Gothenb.," i, 22, 14 (1778), and Geoffroy " Hist. abr. des Ins.," 569, 17 (1764). 

 The latter quotes Reaumur, yet apparently losing sight of the I'estricted habitat on 



* Mr. G. S. Saunders has kindly given me the advantage of his exteii.sive experience in the 

 preparation of minute entomological objects by mounting these and other Coccidm for microscopic 

 examination. — J. W. D. 



C 2 



