36 



REPORT OP THE COMMISSIONER OF AGRICULTURE. 



No. 38. 

 [Magnified.] 



stroyed by the wet and cold -weather and alternate freezing and thaw- 

 ing. These insects, as larva, pupa, and perfect insect, are found gener- 

 ally on terminal shoots and on the under side of leaves, vrhich become 

 distorted and unhealthy from their repeated attacks. The male is 

 •winged, and has a blackish thorax, and is 0.05 to 0.08 in length to the 

 end of abdomen. The female is green, -with a row of black marks down 

 each side, and has no wings, and is rather larger than the male. These 

 insects eject a species of honey-dew, or sweet, sticky substance, from 

 two projecting horns or tubercles on each side of the hinder part of the 

 abdomen, which is greedily eaten by ants and other small insects. 

 ApMs arena, grain or oat-plant louse, does much injury to grain, and 

 " "" especially to oats, but is also found on 



wheat, rye, and other cereals. Their hab- 

 its are much the same as the before-men- 

 tioned plant-lice, excepting that it is said 

 that although their honey-tubea are well 

 developed, these insects emit no honey, and, 

 in consequence, are not followed by ants. 

 It is also stated that they freeze on the 

 stalks in winter and revive in the spring. 

 The colors of some specimens sent for ex- 

 amination to the Department varied con- 

 siderably, some of them being of a lively 

 or dull green, while others were of a de- 

 cidedly brown color. The feet and knees 

 are generally of a darker or- nearly black 

 color ; length, 0.05. 



Aphis gossypii, or the cotton-plant louse, 

 is a great nuisance to the planters, espe- 

 cially when the plants are very small, as 

 then they are more liable to succumb to the attacks of these insects, 

 " "" as by Bucking out the sap they distort 



the stems, and in fact frequently kUl the 

 plants before they have attained suffi- 

 cient maturity and strength to withstand 

 their repeated attacks. Their habits are 

 much the same as the rest of the AiihidcSy 

 and their colors vary from green to a de- 

 cided yellow, striped with black on the 

 upper side of the thorax. A more full 

 description of them may be found in the 

 Patent-Office Agricultural lleport for 

 1855. 



Aphis perslccc is destructive to the 

 peach-tree. Harris says that larva), pu- 

 pa?, and perfect insects live together in 

 crowds under the leaves, causing them 

 by their punctures to become thickened and curled, forming hollows, 

 with corresponding crispy and reddish swellings above, and finally 

 to fall to the ground.. But may not this so-called curl be caused 

 by a fungoid growth or by a sudden change of temperature,^ as some- 

 times the Aphides are not seen until long after the curl has been observed, 

 and frequently not a single plant-louse is to be found in or on the badly- 

 curled and deformed leaves 1 We have, moreover, often observed that 

 this so-called curl appeared almost immediately after very cold nights 

 and warm days in the spring, and the leaves were yet very young and 

 tender. These deformed leaves frequently fall off and are replaced by 



No. 39. 

 [Magnified.] 



c 



