14 PACKARD, NOTES ON 



have not given valid generic characters, with the exception of 

 the labial palpi, the value of which are well known. 



In the thorax also there is a family form, at least, in the 

 Zygasnidae and the succeeding group, the Bombycidae. The 

 comparative length and breadth especially of the meso-scutum 

 and scutellum are of value, as are in a less degree the relative 

 size and position, slanting or vertical, of the flanks of the 

 thorax. But this last character owing to the remarkable con- 

 stancy in the form of the thorax and abdomen of all Lepidoptera, 

 is not often of generic value*. 



I have also found the genital armor most useful in separating 

 genera of moths, but for this purpose alcoholic specimens are 

 necessary so that these parts may be drawn out and dissected. 

 There is however no one general family type to which their 

 great variations of form can be reduced. 



These characters are of special use in locating mimetic forms. 

 The Zygasnidae do not imitate the lower moths, nearly so much 

 as do the Bombycidas. Indeed just as embryologists arrange 

 groups in series by their greater or less resemblance to low 

 embryonic forms, can we arrange animals by the greater or less 

 proportion of mimetic forms in any group. 



Mr. Bates (Linnaean Trans. 1862) has considered that 

 the Heliconidae stand at the head of the Lepidoptera. We 

 venture to question this position of the family from the 

 fact that this family mimics most wonderfully the Zygas- 

 nidse. An instance may be quoted from Stoll of a genus 

 allied to Glaucopis which he calls Papilio Znbina (PI. XL 

 fig. 3.) Judging from the plate simply, the antennae, the 

 neuration and the brown and yellow bands and white spots are 

 unmistakedly Zygasnid ; the general form of the body and of 

 the wings are like Heliconia. Among the Piendae, Colias has 

 a mimetic form in the Australian Heterusia pulchella Koller 

 figured by Herrich-Schaefier. But we cannot think of any other 

 butterfly, or of any Hesperians, Sphingidae or .ZEgeriadas 

 which imitate the lower moths, and therefore we consider this 

 as an argument for the superiority of their rank. On the 



* We might here say, that before we were aware of the use Dr. Leconte had 

 made of the epimeral and episternal pieces in the Coleoptera we had used these 

 parts to good purpose in the hymenoptera, where they are exposed to con- 

 stant variation in genera and groups of genera, as well as families. 



