CHAPTER III. 



THE INTERNAL ANATOMY OF AN INSECT. 

 ( Corydalis corn nfa.) 



The insect chosen for the study of internal anatomy in this 

 course is the larva of Corydalis cornuta. This larva lives 

 under stones in the beds 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, 

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

 time. They are most abundant where the water flows 

 swiftest. 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 the most desirable subject for an 

 elementary study of the internal anatomy of insects that can 

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

 one of our largest insects ; there is a coarseness in its struc- 

 ture, which enables one to study the different viscera with 

 comparative ease ; if 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 vis- 

 ible ; and the ease with which the internal organs can be ex- 



