32 INTERRELATIONS OF PLANTS AND ANIMALS 



wings. Flies are of much importance to man because certain of 

 their number are disease carriers. 



Bugs, members of the order Hemiptera (half wings), have a 

 jointed proboscis which points backward between the front legs. 

 They are usually small and may or may not have wings. 



The beetles or Coleoptera (sheath wings), often mistaken for 

 bugs by the uneducated, have the first pair of hardened wings 

 meeting in a straight line in the middle of the back, the second 

 pair of wings being covered by them. Beetles are frequently found 

 on goldenrod blossoms in the fall. 



Other forms of life, especially spiders, which have four pairs of 

 walking legs, centipedes and millepedes, both of which are worm- 

 like and have many pairs of legs, may be found. 



Try to discover members of the six different orders named 

 above. Collect specimens and bring them to the laboratory for 

 identification. 



Why do Insects live on Plants ? - We have found insect life 

 abundant on living green plants, some visiting flowers, others 

 hidden away on the stalks or leaves of the plants. Let us next 

 try to find out why insects live among and upon flowering green 

 plants. 



The Life History of the Milkweed Butterfly. - - If it is possible 

 to find on our trip some growing milkweed, we are quite likely to 

 find hovering near, a golden brown and black butterfly, the monarch 

 or milkweed butterfly (Anosia plexippus). Its body, as in all 

 insects, is composed of three regions. The monarch frequents 

 the milkweed in order to lay eggs there. This she may be found 

 doing at almost any time from June until September. 



Egg and Larva. - The eggs, tiny h'at-shaped dots a twentieth of 

 an inch in length, are fastened singly to the underside of milkweed 

 leaves. Some wonderful instinct leads the animal to deposit the 

 eggs on the milkweed, for the young feed upon no other plant. 

 The eggs hatch out in four or five days into rapid-growing worm- 

 like caterpillars, each of which will shed its skin several times 

 before it becomes full size. These caterpillars possess, in addition 

 to the three pairs of true legs, additional pairs of pirolegs or cater- 

 pillar legs. The animal at this stage is known as a larva. 



