FAMILY ZYGjENIDIA. 15 



other hand it may be argued that the Zygaenidse are lower 

 than these families, because there are forms among them 

 (Castnia) which imitate the butterflies, others (Alypia) which 

 resemble the (Hesperiadae) and others again (Glaucopis and 

 allies) which resemble the JEgeriadse. Thus the lowest gen- 

 era imitate the lowest family enumerated, while the highest 

 genus Castnia mimics the butterflies. As happily expressed by 

 Professor Dana,* it is " a characteristic of a type of the very 

 highest grade, that it is extensively copied after.'' 



To distinguish Castnia therefore from the Hesperians we 

 look for the square clypeus, and the neuration peculiar to the 

 Castniares. In the lower genera allied to Glaucopis we look at 

 the square clypeus, which is often scutellate, and also at the 

 long slender acute porrected palpi, the pectinated antennae, and 

 also the peculiar neuration which it is difficult briefly to 

 describe. In certain genera of Boinbycidse, allied to Limacodes, 

 which are difficult to distinguish from some Tortricidas, the 

 practiced eye can by the large broad clypeus which carries the 

 insertion of the antennas very high up the front, at once locate 

 the genus. Likewise the large broad clypeus enables us to 

 separate those Notodontians from the Noctuidas, which they 

 resemble. If we could select with safety any single character 

 among the moths upon which to rely, it would be the clypeus. 



The Zyaeginidae are distinguished from the neighboring fami- 

 lies of Lepidoptera by the following characters : the head is of 

 moderate size and entirely free from the thorax, but not so 

 much so as in the iEgeriadas or Noctuidaa. There is a great 

 equality in the size of the three tergal pieces of the head: i. e. the 

 occiput, epicranium and ctypeus. The length of the two first 

 of these pieces taken together is about equal to that of the cly- 

 peus, but more generally shorter, and as among all Lepidoptera 

 the epicranium is the larger and longer. On the flanks of 

 the head, is situated an ocellus just in the rear of the insertion 

 of the antennas, which are inserted on the side of the head, in 

 front of the epicranium which narrows, and is often bilobed be- 

 tween] their bases. In the typical genera the antennas are 

 simple, not setose, and slightly swelled in their middle, or par- 

 tially clavate towards the tips as in Zygaana. Eyes large and 

 globose. ';; The clypeus is nearly square, the sides hardly con- 



* Classification of Animals based on the principal of cepkalization. Amer. 

 Journ. Sc. Jan. 1864, p. 15. 



