CHAPTER III. 



THE INTERNAL ANATOMY OF AN INSECT. 

 Corydalis cornuta. 



The larva of Corydalis cornuta lives under stones in the bed 

 of swiftly flowing streams ; it is well known to sportsmen 

 under the name of " dobson," and is used extensively as bait 

 for black bass. 



As the larval state of Corydalis lasts nearly three years, 

 larvse which are at least two years old may be found at any 

 time. They are most abundant where the water flows swift- 

 est. A good way to obtain them is to hold a dip-net or a 

 wire screen in the stream below some stones, and, lifting the 

 stones with a hoe or garden rake, cause the current to sweep 

 into the net the insects which were under the stones. 



This larva is probably as desirable a subject for an ele- 

 mentary study of the internal anatomy of insects as can be 

 found in this country. The species is a large one, being one 

 of our largest insects ; there is a coarseness in its structure, 

 which enables one to study the different viscera with com- 

 parative ease ; it is furnished with well-developed organs for 

 aquatic respiration, and at the same time with equally well- 

 developed organs for aerial respiration ; and, as already 

 stated, fresh specimens can be easily obtained at any season, 

 even in mid-winter. 



Unfortunately, however, the appearance of the insect is 

 very disagreeable to most people. But after a specimen has 

 been opened and pinned upon cork, as is necessary in the 

 study of the viscera, the disagreeable features are not visible [ 



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