22 UNITED STATES NATIONAL MUSEUM BULLETIN 2 76 



of egg masses collected in the field, or by examination of the spumaline 

 of unspent females, whether they are pinned or preserved. Preserved 

 specimens are easiest to examine since the spumaline remains soft 

 enough so that thin slices can be cut with a razor blade. In pinned 

 specimens the spumaline is hard and brittle, but it also can be ex- 

 amined for specks by cutting thin slices which are more properly 

 termed "chips." These chips must be made as thin as possible since the 

 specks may be difficult to see in thick pieces of heavily pigmented 

 spumaline. Many chips will be unsuitable for this reason, but some of 

 them will be thin and unfractured, so that the more transparent edges 

 can be examined for specks. If specks are numerous they are easily 

 seen with the aid of a dissecting microscope, but if there are only a few, 

 it is essential to have a good, thin, cleanly chipped fragment since they 

 are easily missed. 



The density of the specks is not constant for all egg masses from 

 all localities, but populations of M. calif omicum fragile from the Mojave 

 Desert probably have the most dense and most easily visible specks. 

 Varying densities may be found in the same local population. In 

 most of these cases the egg masses appear to be identical in every re- 

 spect except the density of the specks, and these egg masses are believed 

 to have been laid by motlis belonging to the same species. 



Whenever possible during this study several hatched egg masses 

 were collected for each field collection that was made. Appendix 

 I contains data on the number of egg masses collected at each locality, 

 and whether or not the spumaline contained specks. In some cases no 

 egg masses were collected, either because none could be found, or be- 

 cause it was not deemed worthwhile to spend time looking for them. 



Most of the data suggest that the presence or absence of specks 

 is not related to the host species which the larv^a fed on. For example, 

 in at least eight different locahties (Coll. Nos. 114, 115, 117, and 

 230 of M. calif omicum fragile and 254, 259, 294, and 316 of M. cali- 

 fornicum) some of the egg masses contained specks and some did not, 

 even though all of them were collected on the same host. Of course, 

 there is no assurance that the females which laid these eggs came from 

 larvae which fed on the same host the previous year, but it seems 

 likely since no colonies were found on other hosts in these localities. 

 Also, a check of the females reared from these collections showed 

 essentially the same result; some of the females had specks in their 

 spumaline and some did not, even though the larvae v/hich had de- 

 veloped into these females had all fed on the same host in a given 

 locality, and all had been reared under similar conditions. 



In addition, seven different hosts belonging to four different families 

 were fed upon at these eight localities. If the specks are caused by the 



