1894.] 29 



The late A. Foerster had a theory, which was also supported by 

 the late J. Lichtenstein, that certain similar forms of LecaniidcB, which 

 he enumerated {cf. Ent. Mo. Mag , xxiii, pp. 25, 26), found on different 

 trees, and which have received distinctive specific names, are only one 

 and the same species ; but adverting to the structural discrepancies 

 in the insects, especially in the antennae and legs, which have been 

 discovered in later time, this view is not tenable. Yet trial might be 

 made in a home experimental station, constantly under the survey of 

 an investigator to ascertain decisively whether all Coccids would live 

 on trees totally different from those on which they usually feed. Some 

 can, and do naturally, but they retain all their structural characters, 

 and thus can be identified. 



Lecanitjm hespeeidum and L. lauei. 

 In Lecanium lauri, on which, with the assistance of Mr. Newstead, 

 I gave a note in this Magazine, vol. ii, u. s., with a view to show that 

 it is distinct from L. hesperidum, one special point of dissimilarity is 

 in the structure of the digitules of the feet, and it is further noticed 

 that, in this country, L. hesperidum is found only on orange and 

 lemon trees under glass, and L. lauri only on bay trees. Mr. Maskell, 

 however, has noticed (vol. iv, p. 103) a reverse order, inasmuch as in 

 New Zealand L. hesperidum occurs on laurel, ivy, holly, and other plants, 

 and in Australia L. lauri lives on citrus. This is very curious. The 

 validity of the differences pointed out is admitted, yet the inference 

 that there is a distinction of species is demurred to, and the belief is 

 expressed that there is really but one. I do not wish to have a con- 

 troversy with one who has had long and varied experience in the 

 microscopical investigation of Coccids, but I hardly think that his 

 reasons are conclusive. We come back to the doubt of how much or 

 how little of structural character is sufiicientto determine a difference 

 of species. In Goleoptera and Hemiptera, for instance, a small variation 

 in sculpture, striation, puncturation, hairiness or spinosity, form or 

 length of the joints of antennse or feet, are held to be good differential 

 specific characters. Size and colour do not count for much, and in 

 Lepidoptera especially, where they used to be greatly used to differ- 

 entiate species, they have had to be abandoned as unavailable for that 

 purpose ; yet they still have at times a value subsidiary to considera- 

 tions of structure of adult and larva. With regard to L. hesperidum 

 and lauri there may be the hypothesis that they are representatives of 

 divergence from one prior form, as yet not differentiated beyond the 

 stage of " race," and hereafter destined to become more decidedly 

 separate. 



