94 U.S. NATIONAL MUSEUM BULLETIN 25 6 



portion of Coahuila, and throughout Nuevo Leon and Tamaulipas as 

 far south as Tula in Tamaulipas and Cerritos in the State of San Luis 

 Potosi. It is prevalent between Uvalde, Eagle Pass, and Laredo, Texas, 

 and between Monterrey and Victoria, Mexico, but as with other mem- 

 bers of the genus, its abundance is sporadic in the various districts. 



Along the Rio Grande from Laredo to Eagle Pass and in the foothills 

 north of Uvalde, M. ulkei is encountered in the same fields as M. armata. 

 In the foothills country, where the clumps of prickly pear are rather 

 scattered, the number of adults of both species rarely exceeded more 

 than two or three per plant. Although the two forms are not closely 

 allied, records have been made in this sector of male ulkei copulating 

 with female armata, and of female ulkei W\\h male armata. In the southern 

 portion of Nuevo Leon and adjacent districts in Tamaulipas, the range 

 of ulkei overlaps that of the allied variolare, and the two occur in the 

 same local areas. 



The dominant prickly pear through the region embraced within the 

 distribution of this insect is the shrubby Opuntia lindheimeri. The related 

 0. cacanapa also is attacked, but no other definite host plants have been 

 recorded in America. In Australia M. ulkei breeds sucessfully in the 

 shrub pears 0. inermis and 0. stricta, and in the tree and semitree forms 

 0. tomentosa and 0. streptacantha; in addition it has completed its life 

 cycle in the low-growing narrow jointed 0. aurantiaca. 



There are two generations, or rather one complete and one partial 

 generation, annually. Emergence of adults occurs in spring from the 

 middle of April to the end of May. From eggs laid by these beetles, 

 larvae may develop rapidly and yield adults in 3 to 4 months, but the 

 greater proportion occupies the full 12 months to complete the life 

 cycle. Hence, the autumn emergence of beetles in August and September 

 is numerically smaller than the spring emergence. Beetles can be seen 

 in the field in almost every month of the year. Some of the spring 

 adults survive for 3 to 4 months and are alive when the autumn beetles 

 emerge. Most of the latter die before the winter, but a small percentage 

 survives; adults in the field in January-March would represent over- 

 wintering stock. At Uvalde, Texas, beetles confined in cages in Septem- 

 ber-October were inactive in December and January, resuming feeding 

 in February and were mating in March. 



The eggs appear to be laid at irregular intervals in numbers of 

 from 1 to 5, the latter figure being the highest number of eggs de- 

 posited by one female in 24 hours. Oviposition extends for several 

 weeks or even longer; in Australia a female continued to lay eggs at 

 intervals over a period of 7 months. The greatest number of eggs 

 deposited by one individual has been 74. The duration of the egg 

 stage seems to be influenced by moisture as well as by temperature. 



