MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



59 



The outer exk'ridr edfje of the tube forms a stron;rly chitiuous seuiieirele which, becouiiug thiuuer. finally passes 

 into tlio delicate niemliranous hinder wall. Also anteriorly a delicate membrane appeal's to cover the chitiuous 

 portion. 



AVb have hero in opposition to the weak naked underlip represented by a triangular chitiuous plate in other 

 I.epidopti'ra a true lignla formed by the coalescence of the inner lobes of the second niaxilhe into a tube, as in 

 many llymcuoptera, and with free external lobes ■which correspond to tlie paraglossse of Hymenoptera. 



Walter lias also detected a paireil .structure which he regards as the hypopharyux. As he 

 states : 



A portion of the inner surface of the tube-like ligula is covered by a furrow-like band which, close to the 

 inner side, is coalesced with it, and in position, shape, as well .as its appendages or teeth on the edge, may be 

 regarded as nothing else than the hypopharyux. 



While he refers to Burgess's discovery of a hypoiiharyux in Thinnis arciiijipiis, he remarks that 

 this organ iu the lower Micropterygiute (Eriocephalidiu) exhibits a great similarity to the relations 

 observable iu the lower insects, adding: 



The furrow is here within ooalcsced with the inner side of the labium, and though I see in the entire structure 

 . of the head the inner edge of the ligula tube extended under the epipharynx as far as 

 the mandible, 1 must also accept the fact that here atso the hypopharyux extends to the 

 inouth-openiug as in all other sucking insects with a well-developed underlip, viz, the 

 Dijitera and Hymenoptera. 



Another feature of importance diagnostic of this suborder is the 

 mandibles (fig. .'>), which, in form, size, and the presence of teeth, are 

 closely related to those of the lower mandibulate orders, being, as Walter 

 states, in the form of true gnawing jaws, like those of the biting insects. 

 They ]iossess powerful chitiuous teeth on the opposed cutting edge, twelve 

 to fifteen on each mandible, and also the typical articulating hook-like 

 processes by which they are Joined to the geua, and fit in corresponding 

 cavities in the latter. In Micropteryx and other of the more generalized 

 moths the mandibles iu a very reduced form have survived as functionless 

 vestiges of the condition in Eriocephala. 



Turning now to the head and trunk, we find other primitive characters 

 •correlated with those just mentioned. 



The head is of moderate size, as well as the body, with small compound 

 eyes, and with two ocelli. The occipittd region is well develox^ed, as is the 

 ■epicranium; the clypeus and labrum are of moderate size. 



The generalized nature of the thorax is especially noteworthy. The 

 lirothorax is seen to be very much reduced, the two tergites being separate 

 and minute, not readily seen from above. The rest of the thorax is very 

 long, exhibiting but little concentration. 



The mesothorax is but slightly larger than the metathorax. The mesoscutuni is very short; 

 the scutellum ratiier triangular than scutellate. 



The metathorax is but little shorter and smaller than the mesothorax and reuuirkable for the 

 widely separated halves of the scutum, a neuropterous character (compare Ascalaphus and 

 Corydalus), iu which it differs from Micropteryx. The shape of the scutellum is that of a low 

 flattened triangle. 



As regards the abdomen, attention should be called to the disparity in size and shape between 

 the sexes; also to the male genital armature, which is very large and completely exserted, 

 and reminds us of that of Corydalus, in which, however, the lateral claspers are much reduced; 

 and also of that of certain Trichoptera (Sericostoma, Tinodes, Stenophylax, Hydropsyche, etc.). 

 The venation of both pairs of wings is much as in Micropteiyx. 



The larval characters of this suborder it would be difticult to give, for iu the remarkable larva 

 of Eriocephala calthella, as described and figured in Dr. Chapman's elaborate account, we appear to 

 have a highly modified form, entirely unlike the simple apodous larva of Micropteryx and perhaps 

 quite unlike the primitive stem- forms of lepidopterous larva'. Chapman well represents its form, as 

 we can testify from mounted specimens in a slide kindly given us by him. The body is broad 



Fig. ^. — irandiblo of Erioce- 

 phala calfhdUi; a. a', iuner and 

 outer articulation ; «, cavity of 

 the joint {acetabulum) ; A, end 

 seen from side of llie rutting 

 edire. — After Waiter. 



