MORPHOLOGICAL ADAPTATION IN INSECTS — GRANDI 221 



victims are preferred, and Lepidoptera Limacodidae are sacrificed. 

 The female Chrysidid seeks the cocooned caterpillars, breaks the pro- 

 tective shell with her mandibles, inserts into it the extroflexible tubular 

 part of the gaster, stings and paralyzes the larva, lays an egg on it, 

 and then closes the opening by making use of the scraped matter mixed 

 with secretion of her salivary glands. 



The Hymenoptera here discussed show a characteristic facies ; they 

 are of a brilliant coloration with a very sclerotized integument. 



The Chrysidinae are well known also for their thanatotic reflexes. 

 In akinesia they turn the forebody under the lower surface of the 

 gaster, rolling themselves into a ball. 



Before my researches (1943), the Cleptinae were considered to 

 have a functioning aculeus, and the Chrysidinae a reduced or at least 

 an inactive and involute aculeus, with the exception of those which 

 are parasites of Lepidoptera, and some exotic forms. 



Now we shall examine the structure of the female gaster. Some 

 Chrysidinae (Chrysis L.) and the Cleptinae are solenogastric. In 

 the former the urites externally visible in a state of rest are three 

 (2d, 3d, 4th) ; those invisible and capable of extroflexion are five 

 (5th to 9th) ; in the latter the visible urites are four (2d to 5th) and 

 those extroflexible are four also (6th to 9th). The telescopically 

 evaginable portion of these gasters when completely extended is two 

 or more times as long as the fore portion and presents an exceptional 

 structure; the 7th urosternum (which, as in all Hymenoptera, really 

 forms the subgenital plate) in correlation with the large prolongation 

 of the caudal part of the gaster, displaced from its normal position, 

 has slipped backward, leaving the 7th tergum without an opposed 

 sternum and placed under the 8th urotergum, with which it has thus 

 formed a strange heterogeneous segment. The ovipositor is quite well 

 developed, but its "outer plates" and cranial part of the valvae of the 

 3d pair are long and thin, resembling the ovipositor of Terebrantia. 

 Nevertheless, the valvae of the ist and 3d pairs form what is properly 

 called a sting, the sheath of which, however, is rather short and only 

 about a third of the caudal part of the valvae, at the expense of which 

 it has been formed. Other Chrysidinae studied by me (for instance, 

 Hedychrum Latr., Hedychridmm Ab.,) are instead pseudosolenogas- 

 tric. In fact their 5th to 8th urites form but a little evident complex, 

 which when fully extended does not exceed in length the fore part of 

 the gaster ; the 6th to the 8th urites are a little longer than wide. Here 

 the 7th urosternum is below both the 7th and the 8th urotergum. In 

 all the Chrysidinae examined by me, the 2d to 4th urosterna appear 



