Fig. 296.—Bittacus tipularius holding a fly in its hind legs. Austria. (After Brauer.)
Fig. 297.—Young larva of Panorpa communis. (After Brauer.)
These larvae (Fig. 297) bear a great resemblance to those of the Hymenopterous family Tenthredinidae; they have biting mandibles and palp-bearing maxillae, and show no approach to the peculiar mouth structure found in the Hemerobiidae; there are three pairs of feet placed on the three thoracic segments, and there is also a pair of less perfect feet on each of the first eight abdominal segments, those behind being the larger. The upper surface of the body bears spines, which, however, disappear after the first change of skin, with the exception of the larger processes on the posterior segment, which persist throughout the life of the larva. The larvae are active for about one month; after this they become quiescent, but do not change to the pupa state for several weeks; when this happens they change in form and cannot creep, although their limbs are not enclosed in any pupa case. Brauer also discovered larvae of Panorpa communis at large in numbers in an old tree stump that was quite covered with moss, and contained many ants in the mouldering wood. The ants appeared to be on friendly terms with the Panorpa larvae. The earlier stages of Boreus and Bittacus were also observed by Brauer; they are essentially similar to those of Panorpa, but the larva in Boreus is not provided with abdominal prolegs. The Panorpidae have been separated from the other Neuroptera by certain naturalists as a distinct Order, called Panorpatae by Brauer, Mecaptera by Packard; but in their structure as well as in their metamorphoses they are not so distinct from the Phryganeidae and the Hemerobiidae as to justify this step.
Fossil forms of Bittacus and of Panorpa have been found in amber and in the Tertiary strata, and Scudder has described some forms from Florissant in which there are no cross-veinlets in the wings. Some remains from the English Lias have been referred to Panorpidae by Westwood under the name Orthophlebia, but it is by no means certain that they really belong to the family.
Fam. X. Hemerobiidae—Ant-lions, Lacewing-flies, etc.
Head vertical; maxillae free, with five-jointed palpi; labial palpi three-jointed. Wings subequal in size, with much reticulation, without anal area. Tarsi five-jointed. Metamorphosis great; the larvae with mandibles and maxillae coadapted to form spear-like organs that are suctorial in function. Pupa, similar in general form to the imago, enclosed in a cocoon.
Fig. 298.—Drepanepteryx phalaenoides. Scotland.
The Hemerobiidae are an extremely varied assemblage of Neuroptera; the perfect Insects of the various sub-families are very different in appearance, but the family as a whole is naturally defined by the very peculiar structure of the mouth-organs of the larvae. These Insects have, in fact, a suctorial mouth in their early life, and one of the ordinary biting type in adult life.