ZOOLOGICAL DEPARTMENT. 



301 



NO. 50— ZOOLOGICAL DEPAETMENT. 



THE GRAIN PLANT LOUSE. 



Aphis (Siphonophora) avence. 



The present season is characterized by one of those wide-spread and very 

 damaging insect invasions that is so discouraging to the farmer. I refer to 

 the present onslaught on the wheat crop by the grain aphis or plant louse, 

 Aphis avence. This louse attacks wheat, barley, oats and rye, and is to be 

 found in small numbers on these grains every year. This year occurs one of 

 those terrible attacks that seem to threaten very serious loss. This raid 

 extends from Ohio west to Indiana and north to Grand Eapids, Michigan. 

 Of this much I am certain. I do not know whether it reaches in such over- 

 whelming numbers to other States or not. So abundant are these lice that 

 they have attracted wide attention and awakened serious alarm. For the 

 past two weeks I have received daily numerous specimens of these lice with 

 the inquiry: What is to be the outcome of this attack? I have received as 

 high as fifteen such communications in a single day. 



what is IT? 



This is a plant louse, or aphis, and is very similar to those that attack our 

 house plants, cherry, plum and apple trees (see Fig.), cabbages and hops. 

 Indeed, so numerous are the species of these lice that hardly one of our valued 

 plants but has its plant-louse enemy. These plant-lice (see Fig.) have 



flask-shaped bodies, are 

 usually green or black, 

 though sometimes they 

 are yellow or red, and 

 are usually quite small. 

 In looking at the grain 

 aphis at this season 

 (see Fig.) four forms 

 will be seen : a small 

 wingless louse, a large 

 wingless form — the full 



magnified. Snort lines show natural size, grown apodouS Or wing- 



less louse ; the pupa of the winged louse, which has short wing pads ; and 

 the mature winged louse. We usually find these four forms at some season 

 of the year in all plant lice colonies. Frequently, and this was true a few 

 days ago of this grain aphis, we only find the wingless forms. Later the 

 pupae with wing-pads and the fully developed winged forms are seen. These 

 winged lice are doubtless developed that the lice may spread before their 

 food is wholly destroyed and they confronted by famine. The mature 

 wingless louse of this grain aphis is about one-tenth of an inch long. The 

 winged louse is nearly twice as long to the end of the wings. This louse is 

 not quite as slim as is aphis mali (see Fig.). As will be observed by 



Apple Tree Plant Louse.— Appis Mali. 

 Winged form natural size and much magnified. Wingless form much 



