The Life-History and Anatomy of Butterflies 



and the fluids in the cup of the flower flow up the proboscis and 

 into the bulb. The bulb is also surrounded by muscles, which, 

 when contracting, compress it. The external opening of the 

 tube has a flap, or valve, which, when the bulb is compressed, 



oor 



Fig. 32. — Interior view of head of milkweed butter- 

 fly: cl, clypeus; cor, cornea of the eye; ce, oesophagus, or 

 gullet; fin, frontal muscle; dm, dorsal muscles; hn, lat- 

 eral muscles; pm, muscles moving the palpus (Burgess). 



closes and causes the fluid in it to flow backward into the gullet 

 and the stomach. The arrangement is mechanically not unlike 

 that in a bulb-syringe used by physicians. The process of feeding 

 in the case of the butterfly is a process of pump- 

 ing honeyed water out of the flowers into the stomach. 

 The length of the proboscis varies; at its base and on 

 either side are placed what are known as the maxillary 

 palpi, which are very small. The lower lip, or la- 

 bium, which is also almost obsolete in the butterflies, 

 has on either side two organs known as the labial 

 palpi, which consist of three joints. In the butter- 

 flies the labial palpi are generally well developed, 

 though in some genera they are quite small. The 

 antennae of butterflies are always provided at the ex- 

 tremity with a club-shaped enlargement, and because 

 of this clubbed form of the antennae the entire group are known 

 as the Rbopalocera, the word being compounded from the Greek 



16 



Fig. 33.— 

 Labial palpus 

 of Colias, 

 magnified 10 

 diameters. 



