646 THE STUDY OF INSECTS. 



In breeding these insects from their nests care should be 

 taken not to mistake cuckoo-flies or other guest-insects or 

 parasites for the rightful owners of the nests. The fact that 

 members of each of these classes of insects are common in 

 these nests adds both to the complexity and interest of the 

 study. 



The digger-wasps found in America north of Mexico 

 represent fourteen families. These can be separated by 

 the following table : 



TABLE FOR DETERMINING THE FAMILIES OF THE 

 SPHECINA.* 



A. Pronotum considerably produced backward on the sides reaching 

 the tegulae in the winged forms ; in one family the females are 

 wingless. 



B. Abdomen with the first ventral abdominal segment distinctly 

 separated from the second by a constriction (Figs. 769, 770). 

 C. Intermediate tibiae with two apical spurs; the intermediate 

 coxae contiguous, or but little separated ; females wingless. 



p. 648 MUTILLIDJE. 



CC. Intermediate tibiae usually with a single apical spur, very 

 rarely with two ; intermediate coxae, as a rule, widely sepa- 

 rated ; both sexes winged, p. 649 Scoliid^e. 



BB. First and second ventral abdominal segments not separated 

 by a constriction. 

 C. Hind legs short, the tibiae not reaching to the apex of the 



abdomen, p. 649 Sapygiile. 



CC. Hind legs long, the tibiae reaching beyond the apex of the 



abdomen, p. 650 Pompilid^e. 



AA. Prothorax usually consisting of little more than a narrow 

 collar, the posterior angles not reaching the tegulae ; both sexes 

 winged in all species. 



B. Fore wings with three closed submarginal cells, (Fig. 773, 2d 

 III, Ills , IIL). 

 C. Base of abdomen with a long slender portion (petiolate). 



* This table is based on one given by Mr. Cresson in his Synopsis of the 

 Hymenoptera of America north of Mexico, Philadelphia, Am. Ent. Soc, 



1SS7. 



