596 On Synthetic Types in Insects. 



The Ilepialus argenteomacnlatus of Harris, which is 

 figured in Professor Agassiz's work on Lake Superior, is 

 the type of a number of gigantic moths belonging to 

 Hiibner's genus Gorgopis, in which, in the elongated body, 

 the large, broad, equal wings, and the details of their struc- 

 ture, we find a very unexpected analogue to PulystoEcliotes^ 

 which is also a gigantic member of the family Hemero- 

 biadcSf of which the lace-winged fly, C/trysopa, is an ex- 

 ample. One of the most constant family characters in 

 the Lepidoptcra lies in the relative size of the three pieces 

 that form respectively the base, the vertex, and the front 

 of the head, that are called by authors occiput, epicra- 

 nium, and clypeus. The Bombyces are characterized by 

 the reduced size of the two first-named pieces, and the 

 enlarged area the shield-shaped clypeus presents, which 

 forces the antennse back upon the vertex, and leaves the 

 upright vertical front broad and open. Now in the Hepiali 

 there is the greatest equality in these three parts ; the 

 cly])eus is greatly shortened and curved down beneath the 

 front; the epicranium advances forwards and down the 

 front, carrying the antenna) towards the middle between 

 the eyes. We find just this condition of things in Poly- 

 stcechotes. In both genera the simple antennas are short 

 and feeble, and placed low down the front ; the clypeus, 

 which is shorter than broad, presents in its tranvcrse diam- 

 eter an irregular, narrow, hexagonal figure ; and the eyes 

 are smaller and more globular than usual in both, espe- 

 cially so in Hepialus. The whole head, which in the 

 Bombyces is nearly always small and sunken in the wooly 

 thorax, is in Hepialus unusually large and free from the 

 thorax. 



In the thoracic region the resemblance is still main- 

 tained. In the Lepidoptera the middle ring is greatly 

 devel()j)ed in size over the pro- and in(;ta-llu)rax, while in 

 the Ncuru])tera there is a great cqualily in the three seg- 



