14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



invariably absent. In Basilona imperalis (Ceratocampidae) the pro- 

 boscis still has a tubular shape and shows a food channel. Both ten- 

 torial muscles are present, but no cranial muscle. 



In all saturniids examined, the position of the tentorium in the 

 head — that is, the length of the hypostomal area below the posterior 

 tentorial pits — suggests that the ancestors of these moths had power- 

 ful feeding mechanisms with the tentorial muscles well developed. The 

 antennal muscles in these moths are always large and powerful, and it 

 may be that the great enlargement of the anterior part of the anterior 

 arms results from the need for a large base for these muscles rather 

 than from an effort to lighten the head. However, the latter purpose 

 is unmistakably served. 



Lasiocampidae: The adult of the eastern tent caterpillar, Mala- 

 cosoma americana, was studied as an example of a lasiocampid, but its 

 resemblance to a saturniid was so complete that no new information 

 was obtained. The antennal, proboscis, and sucking pump musculature 

 is illustrated in figure 6 D. 



Boinhycidae: Similar conditions were found in the common silk 

 moth, Boinbyx mori (fig. 7 A). The proboscis is represented by two 

 shapeless lobes. Both pairs of tentorial muscles are present. 



Papilionoidca: Representatives of five families of butterflies were 

 studied, and some interesting differences were found. In the Nym- 

 phalidae and Danaidae the three pairs of proboscis extensors are most 

 perfectly preserved. Figure 1 1 shows the proboscis extensor of Danaus 

 menippe, known as the " Monarch butterfly." All three pairs of 

 muscles are well developed. The musculature of Vanessa atalanta, the 

 red admiral butterfly, closely resembles it, as does also the mourning 

 cloak butterfly, Aglais antiopia, and the great spangled frittillary, 

 Argynnis cyhela. In certain other Nymphalidae, however, the cranial 

 proboscis extensor has been lost. Such butterflies include the viceroy, 

 Basilarchia archippiis, and the common grayling, Cerpyonis alope. A 

 few species of Lycaenidae were also examined. In Lycaenopsis argio- • 

 Ins, the common blue, and Everes cainyntas, the tailed blue, the mus- 

 culature consists of the familiar three pairs. In Chrysophanus hypo- 

 phleas the cranial muscle has been lost, but both tentorial muscles are 

 well developed. 



Thus, in these two families nothing unusual was found. In the 

 Papilionidae and the Pieridae, however, no trace was found of the 

 cranial proboscis extensor, but instead there was a remarkable migra- 

 tion of part of the anterior tentorial proboscis extensor. Inserting on 

 each stipes with the anterior tentorial proboscis extensor but arising 

 on the clypens, between the anterior tentorial arms, there is a single 



