36 NATURE SKETCHES IX TEMPERATE AMERICA 



have the nectar shallowly held in the hollow sepals accessible 

 to a great variety of insect guests. The scent of these flowers 

 is perceived for a distance of several hundred yards ; the paraffin- 

 oids composing it have the peculiar property of increasing in 

 intensity the farther away the perfume floats on the air up to 

 a certain distance, when it finally disperses by diffusion through 

 the air. In view of these facts, it is not difficult to perceive 

 why the nectar gatherers have preference for the basswood 

 flowers. 



How THE Milkweed Profits by the 

 Visits gf its Insect Guests 



N another chapter on the Monarch Butter- 

 fly and its Mimic, I will refer to the 

 familiar banded larva found on the milk- 

 weed. On this plant are also found cer- 

 tain other insects. One can hardly think 

 of the greenish purple umbels of the 

 conunon milkweed without associating with these exquisitely 

 perfumed flowers the red, four-sjiotted beetle, Tetraopes tctra- 

 ophthalmus. This snuill beetle, which has blackish antennae, 

 is often seen in July resting on the leaves, singly or in pairs, 

 as depicted in the colored plate (facing page 36). On sun- 

 shiny days it is also seen flying from one plant to another. 

 The life of this insect is intimately connected with the milkweed, 

 the roots and lower parts of the stems of this plant furnishing 

 nutrition for the larvae which penetrate and feed upon them. 



Besides the almost constant presence of the red, four-spotted 

 beetle, the perfumed flowers entice winged insects of many 

 kinds. These include such forms as bees, wasps, flies, butter- 

 flies, moths, beetles, and occasionally bugs. Guided by the 

 scent, the insects are easily led to the honey. But while the 

 insects are in quest of this food, there is a reciprocal process 

 between plant and guest. At the same time they visit the 

 flowers they perform pollination, which is of great importance 

 to the plant's perpetuation. The dependence of these plants 

 ujKin insects as agents for transferring pollen is shown 

 by the peculiar structure of the flowers, many of them 



