1916] Williams — Life-History of Methoca stygia Say 121 



NOTES ON THE LIFE-HISTORY OF METHOCA STYGIA 



SAY. 



By Francis X. Williams, 

 Melrose Highlands, Mass, 



The Thynnidse, a family of aculeate wasps seems to find its 

 metropolis in Australia. There, many large and striking forms 

 occur — in strong contrast to our own modest species and to those 

 of Northern Europe, represented indeed by the single genus 

 Methoca. The diversity between the two sexes of the same species, 

 in our forms at least, is so great — the male comparatively large, 

 with coarse sculpture, compact thorax and well developed wings — 

 the female small, slender and ant-like, that one does not wonder 

 that they were first placed in separate genera, namely Tengyra 

 and Methoca. 



The Thynnidse have several points in common with their gen- 

 erally hirsute relatives, the Mutillidse, as for example, the apterous 

 condition and ant-like appearance of the female, her long curved 

 sting, hardness of body, and the habit of the male of carrying his 

 mate about in his mandibles, a procedure possible in the Mutillidae 

 however only where the male is much larger than the female and 

 capable therefore of flying about with her. 



I was prompted by the researches of Adlerz ('03, '05) and of the 

 Champions ('14, '15), on the biology of Methoca ichneumonides 

 Latr. of Britain, Belgium, Scandinavia, and other parts of Europe 

 to make observations on our own New England species, Methoca 

 stygia Say, and while meeting with indifferent success, I was able 

 to note that the habits of the two species are very similar. 



Like its European cogener the female varies greatly in size, the 

 series in my collection has its smallest individual 3.75 and its 

 largest 7 mm. long, while the Champions have found M. ichneu- 

 monides to vary from 4 to 9 mm. The male of 31. stygia, Fig. 1, 

 is about 11 mm. long and shining black, with the head and thorax 

 coarsely punctate, and the clypeus with a prominent median tooth. 

 The abdomen is polished and rather coarsely punctate, with the 

 segments, particularly 1 and 2, strongly separated by well-marked 

 constrictions, which are deepest ventrally. The end of the ab- 

 domen is armed with an upcurved ventral spine over which is a 



