The Validity of the Coccid Genus Eulecanium Cockerell.
[Read before the Canterbury Branch, March 29, 1939; received by the Editor, April 26, 1989; issued separately, March, 1940.]
IN the Canadian Entomologist of February, 1901, T. D. A. Cockerell and P. J. Parrot give a table for the separation of the genera of Coccidae related to Lecanium Burmeister, a continuation of a former table published in the same journal in November, 1899. Among the genera and subgenera mentioned is that of Eulecanium Ckll., which is defined as follows:—
|2.||Female convex, usually hemispherical, hard when mature, legs and antenna slender, normal.||6|
|6.||Skin microscopically tessellated, holoarctic group.||Eulecanium Cockerell.|
|Skin with polygonal areas containing pits.||Saissetia Deplanches.|
Cockerell's paper wherein he erects the genus Eulecanium has not been available, but Green (1904), in a supplementary note, states that the type of Eulecanium Ckll. is E. tiliae (Linn.), a species with. which I am unacquainted.
Harry F. Dietz and Harold Morrison (1916) do not recognise the genus Eulecanium, but mention it as a synonym of the genus Lecanium Burm., which they diagnose as follows: “Female circular to oval, legs and antenna fairly well developed; middle spiracular spine less than twice as long as the outer two (except nigrofasciatum); anal ring with eight hairs; hypopigial setae wanting.” They then proceed to describe six species, and in each the genus Eulecanium is placed as a synonym.
Green (1904), in a supplementary note, gives a list of subgenera not yet represented in Ceylon, among which is found the genus Eulecanium Ckll. On going through his species, however, I find two placed in the genus Saissetia which have certain characters found only in the genus Eulecanium. When giving an annotated lift of the Coccidae of Ceylon, Green (1937) further states as follows: “The genus Lecanium itself has been split up and disguised under a multitude of names, some of which I have indicated in brackets. But the boundaries of most of the proposed genera are so indeterminate that it is difficult to assign a species to one or other of them with certainty. The only genus (or subgenus) that is unmistakable is Paralecanium, which is distinguished by a marginal fringe of flabelliform setae.”
It has long been obvious to all who make a study of the Coccidae that the old genus Lecanium has become unwieldy, and, as stated above, the proposed genera are by no means helpful. This fact has been particularly evident to me for the last few months, during which time I have been making a systematic study of the life-history of Lecanium persicae (Fab.).
In the adult instar, owing to the character of the stigmatic spines, this species could not be mistaken for any belonging to either of the genera Coccus or Saissetia. In the larval instar also it differs in the
same way from the species in those two genera. It is in the intermediate instars that difficulty in identification arises, for the insects are then flat, soft, and the stigmatic spines are similar to those of insects of the same stage in both those genera.
Cockerell (1901), in his diagnosis of Calymnatus (= Coccus), states as follows:—
|1.||Female flat or slightly convex, legs and antenna slender, normal.||5|
|5.||Female with marginal hairs, body soft, moderately convex.||Calymnatus Costa.|
|Female with marginal hairs, skin hard, with large tessellations.||Eucalymnatus Ckll.|
On comparing the diagnosis of Calymnatus with that given for Eulecanium, the only distinct difference between the two genera is found to be in the derm of the latter being hard when mature, and microscopically tessellated. One can distinguish between flat and hemispherical, but intelligently to convey the distinction of convex and slightly convex is an entirely different matter; moreover, marginal hairs are present in all the species, and with the exception of the genus mentioned by Green, vary according to the species and not the genus. Even the question of hardness is likely to become a matter of opinion, for it is not until the insect has deposited its eggs that the body becomes hard. There is, again, the tessellation of the dorsal derm, which is apparent only in the natural state, and quite disappears when the insect has been prepared and mounted. As to the number of hairs in the anal ring which, according to the diagnosis of the genus Lecanium given by Dietz and Morrison, are eight in number, these will be found to vary according to the species and not the genus; for while Lecanium (Eulecanium) corni Bouche certainly possesses eight hairs, persicae, which is undoubtedly congeneric with that species has only six, a fact which makes me doubt whether Marchal's (1908) description of the second instar of L. corni, which he states has six hairs on the anal ring, really belongs to that species.
There are only two species in New Zealand—so far as is known—that sometime or other have been placed in the genus Eulecanium, and they are: E. persicae (Fab.) and E. corni Bouche, with both of which I am acquainted. When these two were compared with descriptions of species belonging to many other genera, they were found to possess in common two characters which were never found together in any of the other genera, with the exception of a few species belonging to the old genus Lecanium. These two characters are: the long, subequal, stigmatic spines, and the punctate appearance of the dorsal derm. One or other of these characters may be found in other genera, but not the two together. As to the question of convexity of the dorsum, this is often increased or diminished according to the position the insect, has taken up, and the question of size is equally valueless.
The punctate appearance of the dorsal derm is very distinctive in the mature adults, and is quite distinct from that found in the genus Saissetia. Some few species belonging to the genus Coccus are said also to exhibit this character, but the long stigmatic spines of Eulecanium are absent.
With the exception of Marchal's paper, no mention has been made as to the arrangement of the large multilocular pores found on the ventral surface of the abdomen. I believe these pores to be present in most genera belonging to the Coccinae. They appear to be analogous to those found in the Pseudococcinae and are a sign of maturity, In certain New Zealand species belonging to the genera Ctenochiton Maskell and Inglisia Maskell, it may be possible to use these pores in the separation of the genera, but until further investigations have been made into numerous species belonging to the genera Coccus, Lecanium, Eulecanium, and Saissetia, they will be of specific value only.
Taking into account all the known characters above mentioned, there is no reason why a workable system for the separation of the species under the different genera should not become available, and I beg here to give a generic diagnosis that will definitely place a number of species in Eulecanium as a subgenus of Lecanium Burmiester.
Subgenus Eulecanium Ckll.
Adult females after ovipositing, convex, sometimes hemispherical, dorsum more or less chitinised, usually hard, with numerous small clear areas, round or oval, giving to the body a punctate appearance. Legs and antenna normal, usually slender; stigmatic spines in triplicate, all three long and sub-equal; submarginal tubercules present or absent; small tubular ducts usually present in submarginal bands on ventral surface; large multilocular disc pores present on ventral surface of abdomen; ventral derm spines present or absent; anal complex of normal lecanid form; anal cleft usually well-developed, open. Larva normal, with three very short sub-equal stigmatic spines. Intermediate instars with the central stigmatic spines much the longest.
Dietz, H. F., and Morrison, H., 1916. The Coccidae or Scale Insects of Indiana, Eighth Ann. Rep. Indiana State Ent., April, pp. 250–258.
Green, E. E., 1904. Coccidae of Ceylon, vol. 3, p. 248.
—– 1937. An Annotated List of the Coccidae of Ceylon, etc., Ceylon Jour. Sci., sec. B, Zoology and Geology, vol. 20, pt. 3, Aug., p. 298.
Marchal, P., 1908. Notes sur les Cochenilles de l'Europe, Soc. Ent. de France, vol. 77, p. 285.