INJURIOUS TO MELONS, CUCUMBERS, SQUASH, ETC. 385 



okra, orange, and its occasional food -plants include many others, 

 as it is found on a long list of weeds, most abundantly on shep- 

 herd's purse and pepper-grass, upon which it multiplies in early 

 spring and probably passes the winter. 



Life History. The life history is much the same as that of most 

 of our common aphides, though of some phases we are still in 

 ignorance in spite of the most careful study. The females give 

 birth to from four to ten aphides a day, depending upon the tem- 

 perature and food supply, and these become full grown in from six 

 to eight days. As the affected leaf becomes non-succulent the 

 aphides migrate to another leaf and often cluster on the terminal, 

 which is checked and stunted. As they become more numerous, 

 winged forms migrate to other plants and within two weeks a 

 colony of fifty or more will form the progeny of every one born 

 by the immigrating female. Reproduction seems to go on this 

 way throughout the year, being stopped only by the cold of win- 

 ter, as far as has been observed. No true sexual forms or eggs, as 

 are known to occur with other nearly related species, have been 

 observed, and the viviparous forms have been found throughout 

 the winter in Colorado and Texas. 



Enemies. Fortunately the melon-aphis is subject to the unre- 

 mitting attack of many insect enemies, the list including some 

 thirty-five species. Among the more important are the common 

 ladybird-beetles and their larva?, of which the convergent lady- 

 bird,* the nine-spotted ladybird,! and the spotted ladybird,! 

 shown in Figs. 1-5, are among the most effective, and the maggots 

 of various common syrphus-flies, and the aphis-lions. Even 

 more beneficial are the little parasitic flies whose larva? live within 

 the maggots and destroy myriads of them with incredible swift- 

 ness. The most common of these Tf are the same as the most 

 common parasite of the green bug (Fig. 1 13) , and they often destroy 

 the aphides over a whole field in a few days. They are most effect- 



* Hippodamia convergens Guer. 



t Coccinella Q-notata Herbst. 



J Megilla maculata DeG. Family Coccinellidce. 



Family Chrysopidce. 



1[ Lysiphlebus testaceipes Cress. Family Braconidoe. 



