526 NATURAL HISTORY OF ARTHROPODS. 



The family MUTILLID.E includes the strange insects commonly known as solitary 

 ants, so called on account of their solitary habits and their strong general resemblance 

 to the true ants. Structurally, however, they are much more closely related to the 

 Scoliidae than to the Formicidse. From the latter family they may be readily distin- 

 guished by the total absence of the characteristic knot or knots upon the peduncle of 

 the abdomen. As with other solitary Hymenoptera, there are but two forms, male 

 and female. The females are always wingless, and the males, with but few exceptions, 

 are winged. The females lack ocelli, and are furnished with a powerful sting. In 

 habit the species are in the main diurnal, though the African species of Dorylus are 

 said to be nocturnal. The females run with considerable rapidity, secreting themselves 

 on the approach of danger, and the males often frequent flowers. Mutilla occidentalis 

 digs deep holes in beaten paths and stores them with flies and other insects, while one 

 of the European species is said to live parasitically in the nests of humble bees. The 

 creaking noise made by these insects is supposed to arise from the action of the pro- 

 notuni on the front edge of the mesonotura. A common species in Texas is known by 

 the name of " the cow-killer ant," on account of a popular superstition that its sting 

 is very dangerous to live-stock. 



The family SCOLIIDJE is closely related to the preceding, both in structure and in 

 habits. Both sexes, however, are winged, with rare exceptions, and the females as 

 well as the males are furnished with ocelli. The legs are short and stout, and the 

 antennae are short and thick, and generally convoluted and serrate in the females. 

 The body is sometimes very hairy. The species are frequently of large size, especially 

 in the tropical regions, and abound in sunny, hot, and sandy places. While the 

 majority of the species of this family undoubtedly have the normal fossorial habit ; 

 certain species are supposed to be parasitic. For instance, Passerini found the larva 

 of Scolia flavifrons within the body of the lamellicorn beetle Oryctes nasicornis, and 

 similarly Coquerel states, that Scolia oryctopliaga lives on Oryctes simia in Madagas- 

 car. Sumichrast supposes that the females of Scolia azteca lay their eggs in certain 

 larvae which abound in tan at Tehuacan. Tiphia inornata is a very commonly 

 observed species in the eastern States. It makes perpendicular burrows in sandy soils, 

 and the males are found frequently on flowers. JtJlis quadrinotata and Ells plumipes 

 have been commonly observed on the cotton plant at the south, and are supposed to 

 carry off the larvae of the cotton worm (Aletia xylina}. Myzine sexcincta is a very 

 commonly collected species south of New England. Both sexes frequent flowers, and, 

 although possessing no polleniferous organs, undoubtedly have considerable influence in 

 the cross-fertilization of certain plants. It is very abundantly found upon Syringa. 



The SAPYGID^E is a small family, comprising not more than a dozen European 

 species. The body is generally smooth and slender and ornamented with yellow. The 

 antennae are long and more or less clavate, the head is long and the pronotum very 

 broad. It is well proven that the typical genus Sapyga is inquilinous in the nests of 

 wild bees, commonly of the genus Osmia. The cocoons of Sapyga pnnctata have 

 been found in the cells of Osmia, helicicola, and the female of the same species has 

 been observed entering the cells of Osmia bicornis and 0. ccerulescens. On the other 

 hand we have the old statement of St. Fargeau, to the effect that the females make 



^j ' 



burrows in the mortar of walls or in wood, in which they place their eggs and stores, 

 adding in support of this hypothesis only that he had observed the common S. punc- 

 tata carrying a larva, The eggs of the last-named species are 2.1 mm. long, elongate- 

 oval in form, slightly thickened at one end. 



