NO. 4 FEEDING MECHANISM OF LEPIDOPTERA SCHMITT 5 



are capable of some motion, each palpus having usually one or two 

 muscles at its base, which enable the palpi to clasp the coiled probos- 

 cis or to release it. 



The mouth cavity, or preoral cavity, is defined by Snodgrass (1935) 

 as " an external space bounded anteriorly by the epipharyngeal wall 

 of the labrum and clypeus, posteriorly by the labium, and laterally by 

 the mandibles and the maxillae." The hypopharynx is described as 

 lying in this cavity as a tonguelike lobe. The cibarium is that part of 

 the preoral cavity which is anterior to the hypopharynx ; that is, the an- 

 terior surface of the hypopharynx forms its " floor." The salivary 

 meatus is the portion of the preoral cavity which is posterior to the 

 hypopharynx, i. e., enclosed between the hypopharynx and the an- 

 terior surface of the premeijtum. The median salivary duct pours its 

 secretions into this cavity from a small pocket called the salivarium, 

 between the labium and the hypopharynx. 



In the Lepidoptera most of the cibarium is incorporated with a part 

 of the pharynx in the sucking pump, as will be demonstrated later. 

 There is a small portion of the epipharyngeal surface which is not a 

 part of the sucking pump, and this part is usually applied against the 

 proboscis base. The salivary meatus is practically nonexistent, as the 

 hypopharynx has completely lost its lobular character, and there is no 

 protrusion of a prementum beyond the salivarium. The hypopharynx, 

 in fact, forms most of the " floor " of the sucking pump (fig. i A) as 

 a single well-sclerotized piece. 



II. THE PROBOSCIS 



Savigny long ago discovered that the proboscis of Lepidoptera is 

 derived from the maxillae or rather from one pair of the lobes of 

 the maxillae. The cardo and the stipes are usually quite distinct, and 

 form no part of the proboscis as such ; hence the term proboscis 

 should be reserved for the conveying structure itself. Tillyard (1923) 

 has produced evidence that the proboscis is derived from the galeae. 



Structure and musculature. — Each half or unit of the proboscis is 

 therefore a tube, the lumen of which is continuous with the body 

 cavity through the stipes. Each proboscis unit is rendered flexible by 

 a series of fine rings separated by membrane, as described by Burgess. 

 These rings are absent in nonfunctional proboscides. In the butterflies 

 and higher moths the rings are made up of many small flat circles of 

 hard cuticula, like small beads set in rows. The food channel is also 

 lined with rings, similar but having only about one-third the width 

 of the outer rings. Muscles passing obliquely between the rings were 



