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195 7 The Lepidopterists' News 147 THE STRIATED BAND (LEPIDOPTERA, CHIEFLY ARCTIIDlE) by WILLIAM T. M. FORBES and J. G. FRANCLEMONT The structure now under consideration appears to be limited to the Arctiid~ and a few closely related groups, and even in them is of very erratic occurrence. It is worth considering for practical taxonomy, but has two ex­ asperating features: it may be present or absent in closely related forms, and may take every stage of degeneration; and secondly it is located at a point where it is often difficult to examine, exactly at the point where the hind femur covers it in specimens spread in the usual way, without paying any special attention to the legs. The striated band is located on the anterior side of the metepisternum, sometimes conspicuous on its face, sometimes partly turned over the anterior edge and partly concealed by the back part of the mesothorax. Its typical form is just as the name we use suggests-a band, parallel to the anterior edge of the sclerite, and composed of a series of cross-striations, usually obliquely tranverse to the sclerite, and roughly longitudinal on the axis of the body. In the basic type it is a series of short parallel grooves, each bearing a dark longitudinal scale at mid-length or at its posterior end, and covered in the absolutely fresh specimen by scaling, which is more nearly longitudinal (trans­ verse to the sclerite) than the rest of the scaling. In an average "fresh" speci­ men much of the scaling survives, but there is a scaleless stripe between it and the posterior part of the sclerite; in others the whole striated band is denuded, and in many species the metepisternum is largely denuded of scales. The striations may be either ridges or grooves, but are perhaps most often ridges in the Arctiin~, grooves in the Lithosiinre. In any case the special dark scales lie one each at the low poincs. Between these primary grooves, marked by the special scales, there are very commonly incermediate stri~, mostly in front of the special scales, and in many forms the stri~ on this anterior part of the episternum are steeper and stronger than those behind. The structure appears to have been fundamental in one main subdivision of the Noctuoidea, since it occurs in many Euchromiidre, Arctiidre, both Arctiinre and Lithosiin~, and such isolated types as Callimorpha with Haploa, Argina (in modified form) and Deilemera, but is absent in all the Noctuidre and closely related types, in Asota and the other restricted Hypsid~, the Nolidre, Lymantriidre, and of course all the types with Notodoncid type of tympanum (facing down). The following summary of its occurrence is based merely on superficial study of representative types; it may occur also in some more where it is turned into the groove between meso- and meta thorax, but in this case can hardly be functional. Some species have been passed over since we did not happen to have a specimen where the area was not covered by the hind femur, and no attempt was made to survey the exotic fauna, but we think the fol­ lowing report gives a basically correct picture. In the EUCHROMIIDJE (Syntomidre, Amatidre, Ctenuchid~) as a whole, the band is generally rather weak and frequently absenr. 148 FORBES & FRANCLEMONT: Striated baod Vol. 1 1 : 00s.4-5 Cosmosoma myrodora: Band presumably not functional, the thorax in a reasonably fresh specimen being fully scaled. Roughening on the lower parr of the episternum and some inflation of the sclerite suggest that it is de­ scended from forms with a better organ. Syntomeida: A case where there is striking variation within the genus. In S. epilais and joda there is a short, broad band on the upper part of epi­ sternum, normally denuded; the special scales indicating the primary grooves come every fourth groove. S. ipomcece and syntomoides have a flatter episternum as a whole, and there is no denudation and no stria:. ScePJis (several species) and Lymire edllJardsi: about 15 shallow and widely spaced stria: in a narrow stripe. Ctent.tcha (several species): ~hows a narrow denuded stripe along the posterior edge of the strip, though the stripe itself shows only faint evanescent humps and dents. Et.tcereon carolina: no distinct stripe. Didasys bela; : stripe degenerate but distinct on a very thin almost mem­ branous episternum. Horama texana: about 30 fine and strong stria:. Pset.tdomya minima: A very marked striate band, the individual stria: set at an angle of about 45 0 to the anterior line of the segment. Syntomis phegea: nothing. In sum, the Euchromiid strip tends to be weak, but does not usually wholly disappear; well-spaced primary grooves are the rule, but there are sometimes three intermediates to each primary stria. The very fine and widely spaced primary stria: normal in the Lithosiida: do not occur. LITHOSIIDJE (or Arctiida:, Lithosiina:): All the North American species examined show the same type of strip, though it may be vestigial - a series of fine and shallow primary grooves, each with a single special scale, the surface usually smooth and glossy between them, without intervening second­ aries. They are more numerous in Clemensia, nearly obsolete in Jllice, and we can see none at all in Comacla simplex and Cisthene arida. Hypoprepia and Crambidia, standing near the two ends of the series, are almost typical, and Lycomorpha agrees with Hypoprepia. In some species of Crambidia only the lowermost three or four stria: are really visible, while in C. lithosioides about 8 stria: are closely crowded at the lower end. The Old-World Mil­ to christa group as a whole has a striking modification: the entire episternum is swollen like a bubble, and the striate band runs down across its center instead of lying at the anterior edge; it may be weak, or very large, a;most covering the episternum. Of Lycomorpha, more below. In the Arctiida: in the more restricted sense, the band tends strongly to disappear; thus we cannot find it in Spilosoma, Arctia, Apantesis, Ecpan­ theria with Arachnis, Leptarctia, Hyphoraia, Mcenas (vestalis) , Hyphantria, Estigmene, Seirarctia, Tt.trt.tptiana, Nemeophila, and Platyprepia, in other words the most typical tiger, ermine, and harnessed moths. But most surprisingly there is a very distinct strip in Pyrrharctia isabella (which stridulates-JGF) and Phragmatobia, also a much weaker one in Ph. assimilans. All the Euchcetias group have a strongly swollen episternum, somewhat 1957 The Lepidopterists' News 149 like that of the Miltoehrista group, but with the normal or somewhat weak strip along its anterior edge. This includes Ettehcetias, Tanada (but not Ammalo), Pygaretia, and in a less well developed way, Ettvema. The Ettpsettdosma group all have a very similar strip, with something like 30 stri~, all equal and apparently primary; in Ettpsettdosma itself they are somewhat weak for the group bur still perfectly distinct, and such mar­ ginal types as Neritos and Bertholdia are quite like the others. The Halysidota group tends to have a weaker strip or often none at all; the majority of genera have a perfectly distinct though weak one, as in OpharttS astttr, Ammalo helops, Hemihyalea, Hypoerisias, and !Emilia, in the last distinct only at the lower end. Halysidota itself divides: we cannot find a trace in argentata and earyce, perhaps a trace in mawlata and a little more in tonga, bur a perfectly distinct though weak band in einetipes and tessellrlris. In the Ettbaphe group, including several species both of Eubaphe and Virbia, we cannot find a trace, the scaling of the episternum being complete and regular. In Argina and Utetheisa the scaling is also regular and undisturbed, but denuding uncovers a modification of the sclerite: a mere rough spot in Utetheisa and Argina argus, but a large and complex striate area in Arginr/ eribraria. If the band is in general a stridulating structure, it certainly does not function in the Utetheisa group, for the ridging is always completely covered with a coat of scales. Isolated types: Agorcea mimlta shows an anterior band distinguished by more longitudinal scaling, and separated from the rest of the episternum by a transparent line, bur with no visible ribbing. A. semistria does not even have the zone of modified scaling. Bituryx, like A. minttta, has modified scaling but no stri~ on the chitin. Evidently these have no chance of stridulation. The Spilosoma group, including UMcenas }} vestalis, Diaerisia sannio, vagam, and Nemeophila plantaginis, show some fine and irregular striation on the episternal surface, but nothing that can be called a pattern. Deilemera also shows striation completely covered by scales, while in Tyria jaeobece we cannot find any modification at all. The Callimorpha group, which includes several variant old world species and our own Haploa, show a slender and not very strong but otherwise normal band along the anterior edge of the episternum. No structure representing the striated band in any way has been found in any Dioptid~, Notodontid~, Lymantriid~, Noctuid~, Agaristid~, or Nolid~. All this started from the genus Lycomorpha, which has been universally placed in the Euchromiid~, where its venation looks perfectly normal. How­ ever, the venation of the species of T alara, always placed in the Lithosiid~, is like that of Lyeomorpha; moreover by studying the venation of other Lithosiids, one can arrive at a totally different interpretation of the venation of Lyeomorpha, in agreement with that of Talara. It is that Rs and M) have fused, not Sc and Rs, and that Sc is fused for a long distance with the discal cell, but free toward its apex. These two characters are shown in varying degrees, either alone or together, in other species of Lithosiids.

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