l8o MAINE AGRICULTURAL EXPERIMENT STATION. 1904. 



were attracted by the honey dew, ants were present in the usual 

 numbers; and in August three species of yellow jackets were 

 very numerous about the leaves and upon the ground under 

 those species of aphids which secreted most honey dew. 



The larvae of a drone fly, Eristalis tenax, is never found with- 

 out arousing curiosity. Fig. 46 will show why it is called the rat- 

 tailed larva. This maggot lives in such places as cesspools, and 

 the "tail" is really an extended breathing tube the tip of which 

 the insect elevates into the air and is so able to breathe, although 

 the rest of its body is buried in fluid matter. The adult insect 

 frequents flowers. 



The willow cone gall, shown in fig. 43, is another common 

 object concerning which questions are often asked. This gall is 

 caused by a gnat, Cecidomyia strobiloides, about the size of a 

 mosquito, which deposits an egg in the willow buds early in the 

 spring. The subsequent growth of the willow leaves is abnor- 

 mal and they cluster into a close cone-like object, in the heart of 

 which is a larvel cell (fig. 42) containing the yellowish pink 

 maggot. Here the insect passes the winter, and the adult gnat 

 emerges at the time the willows are budding, about the middle 

 of May here in Orono. 



Robber flies, Asilidce, are frequently brought to the station, 

 their queer shape or peculiar manner attracting attention. Two 

 were found this summer preying upon the cabbage butterfly, 

 Pieris rapce, (see fig. 39) and their rapacious appetite leads to 

 the destruction of many insects, the honey bee among them, a 

 fact not enjoyed by bee keepers. 



Among the most important natural factors in helping to keep 

 injurious insects within bounds are the ichneumon flies. 

 Although the various species differ in size and color, fig. 38 will 

 serve to illustrate the characteristic form of many of these bene- 

 ficial insects. 



The slow-flying Pelecinus, fig. 35, has been common enough 

 to cause considerable inquiry. No detailed studies have been 

 recorded, but it is reported to be parasitic upon the white grub, 

 fig. 45, the young May beetle, fig. 44. 



Other insects important in the economy of nature are the num- 

 erous carrion beetles that dispose of decaying flesh which they 

 find in fields and woods. Fig. 41 represents one large genus, 

 Silpha, of these scavengers. 



