14 BULLETIN 143, UNITED STATES NATIONAL MUSEUM 



4. The tiny Mutillid larva hatches from the egg, and begins feed- 

 ing on its host. It devours the latter and becomes full grown within 

 a few days, and then spins its own cocoon within that of its host. 



5. In the colder latitudes the winter is passed in the prepupal stage 

 within this double cocoon. There is one generation a year. In trop- 

 ical and subtropical regions the generations probably number at least 

 two and perhaps several each year. 



6. The males and females emerge ; the males being winged, seek 

 out the females and mating takes place. The act of copulation re- 

 quires only a few seconds. Bertkau (1884) states that he placed a 

 male and female of Mutilla ephippimn in a glass bottle, that copula- 

 tion took place and that mating lasted 25 minutes. Other observa- 

 tions do not confirm this, the general observation being that mating 

 lasts only for a few seconds. If mating lasted for a longer period 

 it is probable that more specimens would be taken in coitu than there 

 are at present. 



EFFECT OF ENVIRONMENTAL FACTORS ON INDIVIDUALS OF THEi SAME SPECIES 



Many writers on the Mutilliclae have been greatly impressed with 

 their variability and have been led to the conclusion that the group 

 does not present structural characters upon which a reliable classi- 

 fication of the species and genera may be made. While this is true 

 to a certain extent, it is the opinion of the writer that variation in 

 the Mutillids has been greatly exaggerated and that the species of 

 these insects really present good tangible structures which may be 

 used taxonomically. The impression of great variation in this 

 family is partly due to the fact that many good specific characters 

 have been overlooked and very often series of specimens representing 

 five or six different species have been regarded as one species. On 

 the other hand there are some notable variations even in a single 

 species, and these of course have only added to the confusion. The 

 two principal variations to be found among individuals of the same 

 species are, (1) variation in the color of the pubescence of the body, 

 and (2) variation in size. 



A number of species in the genus Dasymutilla have the body 

 clothed with dense pubescence. In several species the color of this 

 pubescence varies from a deep red to a light golden yellow. This is 

 the case in both D. fulvohirta (Cresson) and D. occidentalis (Lin- 

 naeus), and occurs in both sexes. What the causes underlying this 

 variation are, is not known. It can hardly be due to a fading action 

 of wind and moisture, although such a cause is possible. All degrees 

 of this variation occur throughout the range of the species. It is 

 very likely that this variation is brought about by some factor in the 

 environment. 



