88 



HYMENOPTERA 



CHAP. 



unprovided for : as a result many of the helpless grubs died, and 

 others were in a state of starvation, when a strange queen-hornet 

 appeared, associated itself with the comb, and, adopting the orphan 

 brood, nourished them and brought -them to their full size. 



We have already alluded to the fact that, so far as external 

 structure is concerned, there is no great difference between the 

 social and the solitary wasps. Both, too, run through analogous 

 series of forms and colours, and the genus Ischnogaster (Fig. 34) 

 seems to connect the two groups by both its structure and mode 

 of life. The social habits are in many species only inferred, and 

 with greater knowledge will probably prove fallacious as a guide 

 to classification ; indeed we have already said that in the genus 

 Vespa perhaps the most perfectly social of all the wasps there 



is one species that has no worker, 

 and that lives, it is supposed, as 

 a parasite, in. the nests of its 

 congeners. For this species, V. 

 austriaca, it has been proposed to 

 create a separate genus, Pseudo- 

 vespa, on account of this peculiarity 

 of habit, although no structural 

 character has been detected that 

 could distinguish it. De Saussure 

 has stated his conviction that 

 workers do not exist in some of 

 the exotic genera, so that it appears 

 highly probable that \vith the pro- 

 gress of knowledge the present divi- 

 sion between social and solitary 

 wasps will prove 'untenable. 



Eemains of Insects referred to 

 the genera Polistes and Vespa 

 have been found in tertiary strata 



FIG. 35. Masaris vespiformis. A, male 

 B, female. Egypt. (After Scliaum.) 



in various parts of Europe and in North America. 



Fam. 3. Masaridae. 



Anterior wing with two complete sub-marginal cells. Antennae 

 usually incrassate or clubbed at the extremity. Claws dis- 

 tinctly or obsoletely dentate. 



This is a group of fifty or sixty species with but few genera, 



