Insect Study 355 



up to the light before we put it into the skillet, lest we get more meat than 

 vegetable in these viands. The flies, who thus take our greens ahead of 

 us, are perhaps a little larger than house-flies, and are generally gray in 

 color with the front of the head silver-white. These insects ought to 

 teach us the value of clean culture in our gardens, since they also mine in 

 the smooth pigweed. 



References — Manual for the Study of Insects, Comstock. 



LESSON LXXVII 

 Leaf-miners 



Leading thought — The serpent-like markings and the blister-like 

 blotches which we often see on leaves are made by the larvae of insects 

 which complete their growth by feeding upon the inner living substance 

 of the leaf. 



Method — The nasturtium leaf -miner is perhaps the most available for 

 this lesson since it may be found in its mine in early Septem.ber. How- 

 ever, the pupils should bring to the schoolroom all the leaves with mines 

 in them, that they can find and study the different forms. 



Observations — i . Sketch the leaf with the mine in it, showing the shape 

 of the mine. What is the name of the plant on which the leaf grew? 



2. Hold the leaf up to the light, can you see the insect within the 

 mine? What is it doing? Are there more than one insect in the mine? 

 Open the mine and see how the miner looks. 



3. There are three general types of mines: Those that are long, 

 curving lines called serpentine mines; those that begin small and flare 

 out, called trumpet mines; and those that are blister-like called blotch 

 mines. Which of these is the mine you are studying? 



4. Study a serpentine mine. Note that where the little insect began 

 to eat, the mine is small. Why does it widen from this point? What 

 happened in the part which we call the serpent's head? 



5. Look closely with a lens and find if there is a break above the mine 

 in the upper surface of the leaf or below the mine in the lower surface of 

 the leaf? If the insect is no longer in the mine can you find where it 

 escaped? Can you find a shed pupa-skin in the "serpent's head?" 



6. W^hy does an insect mine in a leaf? What does it find to eat? 

 How is it protected from the birds or insects of prey while it is getting its 

 growth? 



7. Look on leaves of nasturtium, columbine, lamb's quarters, dock 

 and burdock, for serpentine mines. Are the mines on these different 

 plants alike? Do you suppose they are made by the same insect? 



8. Look on leaves of dock, burdock, beet and spinach for blotch 

 mines. Are there more than one insect in these mines ? If the insects are 

 present, hold the leaf out to the light and watch them eat. 



9. Look in the leaves of pitch or other thick leaved pines (not white 

 pine), for pine needles which are yellow at the tip. Examine these for 

 miners. If the miner is not within, can you find the little circular door 



