1G 



INTRODUCTION. 



these vary in number, four, for instance, occurring on each 

 side in Calosoma, and eight in Meloloniha. These apertures are 

 usually absent from the front part of the tube which is, some- 

 what wrongly, called the aorta ; near the lateral apertures are 

 folds, called sometimes the alar valves, 

 which assist in the circulation of . the 

 c • S blood ; beneath the dorsal vessel is a 

 delicate membrane and connected with 

 this (which forms a pericardium} are 

 delicate muscles, called the alary muscles. 

 This membrane is fenestrated, and when 

 depressed the blood passes through its 

 pores and thus reaches the heart. 

 — sl.v. The heart, according to Grraber, "is 

 nothing more than a regulator, an organ 

 for directing the blood in a determinate 

 course in order that it may not wholly 

 stagnate, or only be the plaything of a 

 force acting in another way, as, for ex- 

 ample, through that afforded by the body- 

 cavity and the inner digestive canal. At 

 regular intervals a portion of the blood 

 is sucked through the same, and then, by 

 means of the anterior supply tube it is 

 pushed onward into the head, whence it passes into the cavities of 

 the tissues. The different conditions of tension under which the 

 mass of blood stands in the different regions of the body then 

 cause a further circulation." 



Connected with the general system there appear to be smaller 

 pumping apparatuses, by means of which a regular flow of blood 

 is kept up iu the limbs, wings, antennae, etc. (cf. Packard, Text- 

 Book of Entomology, p. 402). 



Fig. 8. — Circulatory appa- 

 ratus of a beetle ; a.v., 

 alar valves; e.g., cephalic 

 ganglion. (After Berlese.) 



The liesjnratory System. 



Burmeister (Manual of Entomology, p. 158) says: — "We 

 shall find the respiratory organs of insects as complex and per- 

 fectly developed as we have found their blood-vessels simple and 

 imperfect. The relations between these systems appear to be in 

 them completely reversed, for the air-vessels intersect the insect 

 body as multitudinously as we find the blood-vessels do in the 

 superior animals." There are no lungs, but the whole body is 

 pervaded with air by means of trachea?, which are tubes of very 

 variable size, those connected with the external openings, called 

 the stigmata or spiracles, being the larger main channels. From 

 these latter smaller channels proceed, and from these again 

 originates a network of still smaller tubes, forming ramifications 

 through all the organs inside the body. 



