c 



The Eversible Glands of a Chrysomelid 

 Larva, Melasoma lapponica'' 



gerson garb 



Introduction 

 It is well known that the larvs of certain insects, notably those 

 of Tenebrionidae, l-'aussidae, Staphylinidae, Malachiidse and Chrys- 

 omelidae, possess segmentally arranged eversible glands, which are 

 supposed to be repugnatorial in function. These are highly devel- 

 oped in the genus Melasoma, of the Chrysomelidae, in which they 

 have been studied by several investigators. In spite of the atten- 

 tion which has been devoted to them, there is no satisfactory mod- 

 ern account of their structure. For this reason, at the suggestion 

 of Professor William A. Riley, I undertook the study of these 

 glands. I used the larvae of Melasoma [L/Vm] lapponica, which is 

 very common on the willows about Ithaca, The insects were fixed 

 in Gilson's mercuro-nitric, in Brazil's fluid, and in Flemming's solu- 

 tion. They were cut six and ten microns thick, and those fixed in 

 the first two reagents were stained with Delafield's haematoxylin 

 iron haematoxylin. 



Occurrence of the Glands 



' <rand eosin, while those fixed in Flemming's solution were stained in 



^__X^in two rows along the dorso-lateral portion of the meso- and meta- 



The glands of Melasoma lapponica are situated in the larva in 



conical tubercles, which are eighteen in number, and are arranged 



'^^thorax and the seven following abdominal segments. The thoracic 



tubercles are somewhat larger than the abdominal ones and contain 



proportionally larger glands. They are present during the entire 



period of the larval stage, disappearing during metamorphosis. 



Historical 

 The existence of these glands was known to DeGeer (1), who 

 In 1775 figured and described the external features of those of 



*Contribution from the Entomological Department of Cornell University. 



^--SS*- 



