14 PRINCIPAL CACTUS INSECTS OF UNITED STATES. 



at the base of a newly-formed joint, so that it is soon broken from 

 the plant. In some cases the joints thus separated from the plants 

 take root upon falling to the ground. As a matter of fact this acci- 

 dental planting by the Moneilema beetles is one important cause for 

 the growth of the prickly pear in very dense clusters around the old 

 plant. 



DESCRIPTION OF THE LARVA OF MONEILEMA CRASSUM. 1 



About 12 mm. long when full grown. Body white, with a dark-brown chitin- 

 ous head and with a pale-yellow semichitinous prothoraeic area. Head trans- 

 verse, rounded oblong, with the labrum, sometimes the labium, and the maxilla? 

 light yellow in contrast to the dark-brown mandibles and occiput. Eyes ob- 

 scured. Antenna? single jointed, very small, placed immediately behind the 

 mandibles. Labrum and clypeus transverse; mandibles large, apically emargi- 

 nate, distant ; maxillary and labial palpi small. Body sparsely covered with 

 brown setae. Prothorax tumid, twice as large as either mesothorax or meta- 

 thorax. Mesothoracic spiracles plain. Abdomen 10-segmented, the last 2 modi- 

 fied, forming the anal region; first 8 segments provided with large, round 

 spiracles; first 6 dorsally prominently bituberculate; first 7 ventrally trans- 

 versely grooved. 



These larva? infest the main stem and older joints of the prickly 

 pear. The gallery is wide and soon becomes blackened. The frass 

 frequently becomes infested with dipterous larva? of various species. 

 The larva? are capable of considerable movement and have been found 

 frequently to travel from one part of the plant to another in order 

 to obtain a better supply of food. After attack the plant appears 

 sickly and shows copious exudations of black sap which becomes so 

 hard that it can be cut with a knife with great difficulty. The ap- 

 pearance of this black exudation is shown in an accompanying illus- 

 tration (PI. IT). 



The larva makes an imperfect cocoon, in which transformation to 

 the pupa takes places. These cocoons consist of an inner layer of fiber 

 of the cactus plant covered with sand. The texture is very firm. 

 They measure 25 by 35 mm. They are generally found just beneath 

 the prostrate joints on the ground. The duration of the immature 

 stages was not determined, but it is evident that there is only one 

 generation during the season. Adults appear most commonly in 

 April and May and in September. 



As the Moneilema beetles are among the more important insects of 

 the prickly pear, it may be necessary to combat them in plantings. 

 Three means of attack are in evidence from the account that has just 

 been given, namely, burning, hand picking, and poisoning. The 

 larva? and cocoons can be destroyed by burning the prostrate portions 

 of the plants. The injury can always be located by reason of the 

 large number of joints and stems that have fallen to the ground. A 



1 Prepared by Mr. W. D. Pierce. 



