282 



MANUAL OF ELEMENTARY ZOOLOGY 



g 7 ,rm. 



structure with the way in which they are used. In some 

 cases, as in beetles, they are not very unlike those of the 

 cockroach, and are used for biting the food. In others, as 

 in bugs and flies, they are adapted for piercing the bodies 

 of other organisms, animals or plants, and sucking their 

 juices, the labium forming a tube in which lie the other 

 parts in the form of slender knives or needles. In 

 butterflies the maxillae are long and grooved, and placed 

 against one another so as to form a tube or proboscis 



through which 

 nectar can be 

 sucked from 

 flowers, the other 

 mouth-parts being 

 vestigial with the 

 exception of the 

 labial palps. In 

 bees the mouth- 

 parts are adapted 

 for biting and 

 sucking, the man- 

 dibles being not 

 unlike those of 



d.ej. 



Fig. 186. — A semi-diagrammatic view of the 



hinder part of the body of a male P. ameri- , , 



cana dissected from the right side to show a , c OCKroacn, and 



the generative organs. 



j Anus ; can., anal cerci ; cgL, conglobate gland ; 

 d.ej., ductus ejaculatorius ; gap., gonapophyses ; 

 m.s.g., mushroom-shaped gland; rrn., rectum; st.q, 

 ninth sternum ; stl., style ; t., testis ; v.def., vas 

 deferens ; 6-ro, terga. 



the laciniae of the 

 maxilla blade- 

 like, while those 

 of the labium form 

 a grooved struc- 

 ture, along which 

 liquids can be drawn up. Wings are occasionally absent. 

 They may both be gauzy and used in flight, or, as in beetles, 

 the first pair may be hard and horny and form a case for 

 the second, or, as in flies, the first pair alone may be used 

 in flight and the second pair represented by two minute 

 balancers or halteres. In butterflies both pairs are covered, 

 like the rest of the body, with little scales, which can be 

 brushed off as a powder. 



The life-histories of insects are of three types, (i) In 

 certain cases, known as Epimorpha, the young differ only 

 slightly from the adults, into which they change gradually 



