ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 373 



set horizontally and are much longer than broad ; they are so arranged 

 that the clefts between the separate plates are covered over as com- 

 pletely as possible ; in Vanessa, the marginal plates are beset with 

 lateral teeth. In Pieris, the last eighth of the proboscis has its plates 

 smaller, and their course is oblique and upwards, instead of horizontal ; 

 the spaces between the plates are larger, but a compensation is aflfbrded 

 by the development of spines. The differences which obtain in various 

 Lepidoptera are noted, but in all it is clear that a maximum of 

 strength obtains with a maximum power of movement. 



The mechanism of sucking may be thus described : — When a 

 butterfly thinks it has lit upon suitable food it tests it with the 

 tactile corpuscles of the protruded proboscis, and then slips the top of 

 the proboscis into the fluid ; with this it mixes a certain quantity of 

 saliva. The frontal, lateral, and dorsal muscles contract, and so draw 

 up the operculum of the pharynx ; by this means a large cavity is 

 formed. At the same time the elevator muscle of the oral valve con- 

 tracts, and the oral and proboscidial canal are put into communication 

 with the pharynx, which is almost empty of air. The pressure of the 

 atmosphere drives the fluid into the canal of the proboscis. As the 

 opercular muscles relax, the longitudinal and transverse muscles con- 

 tract, and by this means the fluid is forced into the oesophagus. When 

 the latter muscles relax, the opercular muscles come together, 

 the oesophageal valve closes the hinder opening, the oral valve rises, 

 and a second stream of fluid enters the pharynx. These acts follow 

 one another so quickly and so regularly that a continuous stream enters 

 the canal of the proboscis. It will be seen that the author's account 

 differs from that of preceding writers, and he is, apparently, justified 

 in contending that it is the only one which falls in with the anatomical 

 facts. 



Malpighian Vessels of Lepidoptera.* — M. Cholodkovsky has lately 

 added Tineola biselliella to the list of the few insects that are known 

 to have only two Malpighian vessels ; these are of some size, and are 

 folded along the course of the digestive canal, and end by a distinct 

 enlargement, Suckow has described four Malpighian vessels in a 

 species of Pterophorus, and of Hyponomenta, but later investigations 

 show that they really agree with the great majority of the Lepidoptera 

 in having six. As embryological research has shown that a small 

 number of Malpighian tubules is a primitive character, and that with 

 progressive development the number increases either by branching 

 or by histolysis, succeeded by a fresh development of a larger number, 

 it is clear that the Microlepidoptera in which there are but two, 

 while their caterpillars have six, exhibit just the reverse to what we 

 should expect — or, in other words, we have here a case of atavism, and 

 one which, as it obtains in the imaginal state only, is a periodic rather 

 than a constant atavism. 



Abdominal Muscles of the Bee.f—G. Carlet distinguishes three 

 regions in the abdominal musculature of the bee — dorsal, lateral, and 



* Comptes Rendus, xcviii. (1884) pp. 631-3. 

 t Ibid. (1883) pp. 758-9. 



