DISTRIBUTION 01-" I.. UNDECIMLINEATA. 15 



habitat formation a region which, in the mountainous parts of the country, 

 is frequently wanting altogether, and when present is usually narrow and 

 level and deeply cut by tributary streams. The food plant of this beetle 

 grows from the edge of the river to the talus slopes, and even far up on the 

 hillsides; and, while stray beetles are often found in locations where envi- 

 ronmental conditions are adverse, the characteristic, well-developed colonies 

 are never thus located, because any extended existence and development in 

 these places is not possible. 



The distribution of L. undccimlineata is in isolated colonies and it does 

 not occupy the wide range of habitats that its food plant does. The isola- 

 tion is strikingly apparent to one searching for these beetles, wide stretches 

 of country often existing between the colonies. When found the insects are 

 usually numerous, and I have often been able to collect from 100 to 300 

 specimens in a short time within a radius of a few feet. 



From these colonies dispersion occurs by flying aud not by any means of 

 transportation that I have been able to discover. This flight is observed to 

 begin at the opening of the rainy season, when the insects emerge from 

 aestivation, to continue slightly during the rainy season, and to increase 

 greatly toward its close. 



An instructive illustration of the manner in which the dispersion of this 

 beetle takes place was afforded by the recent building of a railroad through 

 a perfectly flat, frequenth- flooded savanna near Tierra Blauca. The food 

 plant grows generally over the savanna, but the beetle is entirely absent, 

 excepting at a few points along the road where the work of constructing 

 ditches to keep the road-bed intact has created new localities with favorable 

 conditions for their existence. Over a distance of about 18 kilometers there 

 are now located flourishing colonies at each place where the work of the 

 railroad builders has made existence possible, while on the unmodified 

 savanna I have not been able to locate a single colony, and doubt if there 

 are any. In this instance the advance into a new area has occupied two 

 years and has been rapid. That transportation did not bring about the 

 starting of these colonies is certain, as the work of railroad construction 

 was entirely suspended during the rainy season, when the beetles are active 

 aud dispersion takes place. It is perfectly clear that in this case the distri- 

 bution was brought about by some few individuals from a colony happening 

 by chance to discover the newly created habitat, proper for aestivation and 

 for the breeding of the next generation. In each generation many will 

 perish b\' not being able to reach the proper habitat after once having aban- 

 doned the parent colony, but the fact remains that some do discover proper 

 habitats, and when such are found new colonies are established. In this 

 way, in regions where previously existence was impossible, as in the case of 

 the savanna described above, new colonies are established. In the case of 

 the savanna near Tierra Blanca the production of favorable locations was, 



