314 WHEELER— ANT LARVAE. 



filter. Even in the case of the hypodermal glands fatty liquids are 

 known to pass through the thin chitinous cuticle with which the 

 secreting surface of the cytoplasm is always covered, even where the 

 ends of the ducts are intracellular. 



In this connection attention may be called to a very similar exu- 

 dation of blood plasma charged with certain substances {e. g., can- 

 tharidin) through the hypodermis and cuticle in many IMeloid, 

 Cantharid, Lampyrid, Coccinellid and Chrysomelid beetles. It has 

 long been known that when these insects are roughly handled they 

 discharge from the articulations of their legs a white, yellow or 

 greenish, bad-smelling liquid, which Magretti (1881, 1882), Lutz 

 (1895), De Bono (1889) and Berlese (1909) have shown to be 

 blood plasma. It accumulates in pockets at the articulations after 

 passing through the integument and leaving the blood cells (amoebo- 

 cytes) behind, and is clearly an exudate though it is repugnatorial 

 instead of having an alluring or nutrient function like the blood 

 plasma of Pachysima. 



It is unnecessary, however, to seek confirmation of my inter- 

 pretation of the circumoral appendages of the Pachysima larva by 

 merely pointing to the conditions in the Meloids, Coccinellids, etc. 

 Wasmann, Holmgren and Tragardh have published valuable studies 

 of exudate organs much more like those of the ant larvse. To Was- 

 mann (1903) belongs the credit of having first made an extensive 

 investigation of the trichome glands and exudatoria of numerous 

 myrmecophiles and termitophiles. Many of these structures are 

 more or less modified hypodermal glands with tenuous ducts open- 

 ing at the base of hairs (trichomes) which either dift'use'.the secre- 

 tion so that it can evaporate quickly or spread it out so that it can be 

 readily licked up by the ants, but in such termitophiles as the Staphy- 

 linid beetle Xenogaster inflata, the fat-bod}^ in certain parts of the 

 abdomen forms " blood tissue," which becomes the " exudate " by 

 passing through a layer of hypodermis at the base of papillae 

 ("exudate buds").'"' The latter seem to consist of cuticular sub- 

 stance perforated by delicate canals that conduct the exudate to the 

 surface. Wasman says : 



The exudate of these buds seems therefore to be a component of the 

 blood fluid, which is as it were fikered through the hypodermal layer. 



^ The trichome glands may be compared with similar structures in other 



