528 



NATURAL HISTORY OF ARTHROPODS. 



Fig. 654. — PompUius formosus, tarantula-killer. 



lapse of several years, the spiders were still limber and showed no signs of decomposi- 

 tion. This species has but one annual generation, and the adults issue in June. They 



feed by preference from the blos- 

 soms of Asclepias quadrifolia, 

 which blooms in Texas through- 

 out the summer. PompUius 

 natalensis is one of the most 

 beautiful species of this genus. 

 Its head and thorax are velvety 

 black, anteniiiu yellow, fore legs 

 and tip of abdomen brilliant 

 red, and wings gold-yellow. In 

 Natal it is almost domestic, fly- 

 ing in and out of the houses, 

 capturing the house-spiders, and 

 making its nests before the door 

 or under the veranda. 



Agenia and Priocnemis are 

 allied genera. The females of 

 the former build little barrel 

 shaped cells of clay, which may 

 be found under the bark of trees, in the crevices of walls, and sometimes in sand bur- 

 rows. Agenia bombycina makes its cells under prostrate logs in South Illinois, while 

 the allied A. subcorticulis preferably selects a 

 position under the loosened bark of standing 

 trees. Si)ecies of the 'parasitic genera Ptero- 

 malus and Mesostenus have been bred from 

 these cells by Walsh. 



The family Sphegid^ is a group of large 

 extent and of considerable diversity of char- 

 acter. It includes the eight sub-families, 

 Laninse, Spheginse, Mellininae, Bembecinae, 

 NyssoninsB, Philanthinae, Pemphredoninae, and 

 Crabroninae, nearly all of which have been con- 

 sidered at one time or another as having family rank. As already stated, the Sphegidae 

 are separated from the rest of the digger wasps by the pronotum, which does not ex- 

 tend to the base of the wings. 



The sub-family Larrinas is of small extent, and is composed of insects of small size, 

 rather slender form, ovoid-conical abdomen, and with a single spine at the base of the 

 middle tibiffi. The mandibles are notched exteriorly near base, and the labrum is 

 concealed. Although the European and North American species of Larrada and 

 Tachytes are said to be burrowers in the ground, particularly in sandy soil, a Brazilian 

 species of Larrada is said by Mr. H. W. Bates to form for itself cells composed 

 apparently of the scrapings of the woolly texture of plants, resembling bits of sponge 

 or German tinder, and att.'ielied to leaves. The anterior tarsi of this species differ 

 decidedly from those of the burrowing species and indicate well the difference in habit. 

 Tachytes aurulentus frequents the blossoms of Asclepias, and is often found with the 

 pollen masses attached to the hairs of its tarsi. The tarsus figured by Packard in his 



Fig. 655. — Jgenia bombycina and cell. 



