Insect Study 



411 



One of the most remarkable things about the Colorado potato-beetle 

 is its history. It is one of the few insect pests which is native to America. 

 It formerly fed upon sandbur, a wild plant allied to the potato, which 

 grows in the region of Colorado, Arizona and 

 Mexico, and was a well behaved, harmless in- 

 sect. With the advance of civilization west- 

 ward, the potato came also, and proved to be 

 an acceptable plant to this insect; and here 

 we have an example of what an unlimited 

 food supply will do for an insect species. The 

 beetles multiplied so much faster than their 

 parasites, that it seemed at one time as if they 

 would conquer the earth by moving on from 

 potato field to potato field. They started on 

 their march to the Atlantic seaboard in 1859; 

 in 1874, they reached the coast and judging by 

 the numbers washed ashore, they sought to fly 

 or swim across the Atlantic. By 1879, they 

 had spread over an area consisting of more 

 than one-third of the United States. 



Reference — ^The Colorado Potato-Beetle, 



Pupa of potato-beetle, 



enlarged. 



Photo by Slingerland. 



Chittenden, Bulletin of U. S. Department of Agriculture. 



LESSON XCII 

 The Colorado Potato-beetle 



Leading thottght — ^The Colorado potato-beetle is a very important 

 insect, since it affects the price of potatoes each year. It is disagreeable 

 as a food for birds, because of an acrid juice which it secretes. We should 

 learn its Hfe-history and thus be able to deal with it intelligently in pre- 

 venting its ravages. 



Method — The study of the potato-beetle naturally follows and belongs 

 to gardening. The larvae should be brought into the schoolroom and 

 placed in a breeding cage on leaves of the potato vine. Other plants may 

 be put into the cage to prove that these insects will only eat the potato. 

 The children should observe how the larvae eat and how many leaves a 

 full grown larva will destroy in a day. Earth should be put in the bottom 

 of the breeding cage so that the children may see the larvae descend and 

 burrow into it. The adult beetles should be studied carefully, and espe- 

 cially, the children should see the excretion of the acrid juice. 



Observations — i. At what time do you see the potato-beetles? Why 

 are they more numerous in the fall than in the spring? Where do those 

 which we find in the spring come from? What will they do if they are 

 allowed to live? 



2. What is the shape of the potato-beetle? Describe the markings 

 on its head. What color are its eyes? Describe its antennae. How are 

 they constantly used? Can you see the palpi of the mouth? Give the 

 beetle a bit of potato and note how it eats. 



3. What is the color of the shield of the thorax' Describe the legs. 

 Do you think the beetle can run fast? Why not? How many segments 

 has the foot ' Describe the claws. Describe how it chngs to the sides of 

 a tumbler or bottle. 



