THE PLAGUE GRASSHOPPER PARASITE.

Masicera pachytili Skuse.

(Fig. 258.)

General Appearance. The adult flies are somewhat smaller than the ordinary house flies and dark gray in color with white face and light halteres.

FIG. 258. The plague grasshopper parasite (Masicera pachytili Skuse). A'. natural size; A, enlarged.

Distribution. This fly was introduced into California by Geo. Compere from Australia, where it does great execution on the plague locust or grasshopper. To what extent it has become established is not known.

Hosts. Works upon grasshoppers.

Peleteria robusta Wied.

(Fig. 259.)

General Appearance. The adults are about one half inch long. The

face is white; antennæ brown and black; eyes brown; thorax metallic black and dull grayish along the sides; the abdomen brick-red or yellowish with black dorsal and median longitudinal stripe.

Distribution. Common throughout the entire State, having been reported from Lake, Santa Cruz, Calaveras, Los Angeles and San Bernardino counties.

Hosts. This species works upon the larvæ and pupæ of the tussock moth (Hemerocampa vetusta Boisd.) and other moths.

Paradejeania rutilioides Jaen.

(Fig. 260.)

General Appearance. The adult of this species is large, measuring nearly three fourths of an inch in length. The abdomen is especially large and covered with long black hairs. The face is black with a

silvery luster; eyes dark brown; antennæ black; thorax black with yellow margin and scutellum; basal half of the abdomen yellow with a longitudinal median line and the apical half black; wings dusky throughout with yellow base; legs black.

Distribution. Throughout the central and southern parts of the

State.

Hosts. Caterpillars.

BEES, WASPS, GALL-FLIES, SAW-FLIES AND ANTS.

This is without doubt the most important order of insects known, comprising not only the most beneficial insects like the honey bees and parasitic insects, but some very injurious forms like the sawflies and Argentine ant. The transformations are complete, the larva being maggot or grub-like and the pupa quietescent. The adults usually have four well developed membraneous wings and are powerful fliers, but a great many members have no wings at all. The mouth

parts are for biting or modified for lapping. There is a very extraordinary phenomenon of sex abortion and the development of a sting in the females of certain families, while the phenomena of virgin-birth and the formation of galls are no less wonderful.

Due to the great specialization of the members, this order is extremely complicated and no attempt at classification will be undertaken here, and only a very few of the families will even be represented.

TRUE PARASITES.

Of the beneficial insects, by far the most effective are the true parasites belonging to the superfamilies Ichneumonoidea, Cynipoidea, Chalcidoidea and Proctotrypoidea. Not all of the members of these superfamilies are beneficial. Some prey upon seeds as the seed chalcis and

FIG. 261.-Soft brown scale (Coccus hesperidum (Linn.), showing exit holes of true parasites. (After Quayle. Courtesy Cal. Exp. Sta.)

many others upon beneficial predaceous and parasitic insects. And not all the true parasites belong to these four superfamilies, for as we have seen many dipterous insects are very efficient parasites. In all the superfamilies, except the Ichneumonoidea, many of which are quite large, the members are usually exceedingly small; a hand lens or microscope being necessary for the study of them.

The females usually deposit their eggs within, beneath or attached to the outer surface of the host or within the egg, by means of an ovipositor specialized for such purposes. Upon hatching, the young legless larvæ begin feeding upon the body or juices of the host or egg;

the vital tissues of the former being reserved until the larvæ are nearly ready to pupate.

The entire larval period is passed within or upon the host. The pupal stage may be passed within the host or attached or not attached to it.

There are great variations in the time of development, there being but one generation a year in some and many in others. The adults are usually four-winged insects with quick power of flight and great

FIG. 262.-Mummied bodies of the citrus aphid (Toxoptera aurantia Koch), showing exit holes of the internal parasites. (Essig, P. C. Jr. Ent.)

activity. Many of the smaller species have the ability to jump not unlike fleas.

The work of all true parasites is rather spasmodic because of the very nature of their existence. Naturally with the decrease in the numbers of the hosts, the parasites die from lack of food and may be so reduced in numbers that they are not able to check the rapidly increasing numbers of the hosts and a plague of grasshoppers, army worms or scale insects may result.

Unfavorable weather conditions and the work of secondary parasites are also often responsible for the poor showing of these beneficial friends.

PARASITE OF THE COMMON MELON APHIS.
Aphidius testaccipes (Cresson) (Family Braconidæ).*
(Lysiphlebus testaceipes Cresson.)
(Fig. 263.)

General Appearance. The adults are exceedingly small to develop within the bodies of the plant lice, being but seven hundredths of an inch long. The bodies are very slender, dull or shiny black, with legs,

FIG. 263.-Aphidius testaceipes (Cr.) on left; Charips xanthopsis (Ashm.) on right. A, wings; B and C, antennæ; D, abdomen of female; E, abdomen of male. (Essig, P. C. Jr. Ent.)

antennæ and base of abdomens pale amber. The wings are hyaline and iridescent with pale amber stigma. The adult females of these true par

*The writer is indebted to Harry S. Smith for information concerning these hymenopterous parasites, and for aid in placing them in the proper families.