24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 97 



sucking pumps of other saturniids have about the same development 

 as in Samia. 



Boinbycidae: The well-known silk-moth, Bombyx mari, also has 

 a very feeble sucking pump (fig. 7 A). The remnants of only two 

 pairs of muscles are present, one pair being pharyngeal dilators. 



C eratocampidae : The sucking pump of Basilona imperaJis is very 

 weak and in general much as in the saturniids. There are two pairs of 

 pharyngeal dilators. 



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

 soma americana, was studied as an example of this family (fig. 6 D). 

 The pump has a single pair of pharyngeal dilators and three pairs of 

 cibarial dilators, but all are mere threads. 



Hesperiidae: The skippers have well-developed sucking pumps, not 

 unlike those of the butterflies. The head of Epargyreus tityrus is 

 illustrated in figures ii C and 7 D. There is only a single pair of 

 pharyngeal dilators, most of the contraction being provided by the 

 anterior muscles. 



Papilionoidca: The swallowtail butterflies have a large sheet of 

 muscle on each side of the pump, as well as a pair of median muscles 

 and a pair of pharyngeal dilators. In the family Pieridae the pump 

 very much resembles that in Papilionidae, except that two pairs of 

 pharyngeal dilators are usually present. The Nymphalidae and Danai- 

 dae show one or two pairs of pharyngeal dilators ; in Argynnis cybele 

 the dilators of the pharynx originate as two pairs but insert practically 

 as one. The sucking pump of Danaus menippe is illustrated in figures 

 8B and 12 A. 



However, throughout the families of the Lepidoptera it is probable 

 that these pairs of pharyngeal dilators do not represent original pairs of 

 muscles immediately homologous with the dilators of the pharynx of 

 such insects as Dissosteira. For example, in Dissosteira there is a pair 

 of retractors of the mouth angles encircled by the frontal connectives, 

 but it is improbable that any of the muscles encircled by the frontal 

 connectives in Haematopsis are exactly homologous with the retractors 

 of the mouth angles (see fig. 8 A, rao). 



IV. THE LABIUM 



The structure and limits of the labium in adult Lepidoptera have 

 been previously described by other writers, most recently by Snodgrass 

 (1935). In figure 12 B the labium of Hemaris thyshe is illustrated. 

 In this case the labium is limited to a median strip passing to the base 

 of the proboscis, and a small area around each labial palpus. Pos- 

 teriorly, the labium is supported by a hypostomal bridge (HBr.). 



