aconeadj.
/ˈeɪkəʊn/, U.S. /ˈeɪˌkoʊn/ Zoology.
Of the compound eye of certain insects: formed of ommatidia having transparent cells below the lens, rather than a crystalline cone or a pseudocone; (also) designating or relating to ommatidia of this type. Cf. eucone adj.
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the world > animals > invertebrates > phylum Arthropoda > class Insecta > parts of insects > [adjective] > of head > relating to eye > without cone
acone1885
1885 S. J. Hickson in Q. Jrnl. Microsc. Sci. 25 229 The pseudocone, according to Grenacher, differs from the ‘eucone’ and ‘acone’ in possessing the following characteristics.
1888 G. Rolleston & W. H. Jackson Forms Animal Life (ed. 2) 502 In acone eyes one cell stands in the centre with the six others around, and the visual rods or rhabdomeres are contained one in each cell.
1905 Proc. Acad. Nat. Sci. Philadelphia 57 146 The acone ommatidia have no clear refractive substance differentiated in the cone cells, and are considered as the primitive type of eye.
1947 Proc. Royal Soc. B. 134 259 According to his description of the crystalline cone, the eyes would belong to the acone type.
1998 R. F. Chapman Insects (ed. 4) xxii. 591/1 The Semper cells do not produce a separate lens,..but their cytoplasm is clear and they occupy the position of the cone. These acone eyes are present in various families of Coleoptera,..in some Diptera and in Heteroptera.
This entry has been updated (OED Third Edition, September 2009; most recently modified version published online December 2021).
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adj.1885