We found out on 8/7 that one of wild caught Red Admiral (Vanessa atalanta) chrysalises collected on 7/25 was parasitized by a ton of parasitoid wasps (possibly a Pediobius spp.) and today they emerged.

We're not exactly sure what species of parasitoid wasp this is, but we took a few pictures of them. There were possibly hundreds of them inside of our wild caught Red Admiral (Vanessa atalanta) chrysalis. Within a day of emerging, they began mating with each other directly in the petri dish we put them in. The larger ones are clearly females and the smaller ones are males. 

- Brian

Today as we were out picking thistle leaves, our Painted Lady caterpillar (Vanessa cardui) was killed by a European Paper Wasp (Polistes dominula)!

Ever since the European Paper Wasp (Polistes dominula) population exploded sometime last month when summer started, we have been having a huge problem with them killing our insects. This is not the first post that we have made about them (see here).  They actively search all suspect host plants from sun up to sun down and any living arthropod on the plants they search are doomed, large or small, unless they have some sort of defense such as a nest. The wasps seem to rely heavily on smell and are incredibly adept at discerning which plants tend to have defenseless caterpillars (milkweed [Asclepias] and fennel [Foeniculum vulgare] are favorites; on another note, they rarely go for trees).

They are very clever and will find their way into a rearing sleeve or bag if they are determined to attack what is inside. This year they have decimated our Monarch caterpillars (Danaus plexippus) and Anise Swallowtails (Papilio zelicaon) in rearing sleeves, attacked our Anise Swallowtail butterflies in an ovipositing enclosure, and even injured one of our Mediterranean Katydids (Phaneroptera nana) in a screened up enclosure. With this kind of killing power, they are undoubtedly the number one cause of mortality in caterpillars by predation. 

And today they found another victim to add to their list: our fifth instar Painted Lady caterpillar (Vanessa cardui) that we had found at Tilden Regional Park on 7/9. The older of the two we had found already pupated on 7/18 but the other one still had another day or so. But when we were picking some Milk Thistle (Silybum marianum) in our backyard for it, we made the bad mistake of leaving the caterpillar out unprotected. During the two minutes we turned our backs to pick, a European Paper Wasp came by and attacked. By the time we saw, the wasp had already bitten a whole in the caterpillar and within seconds, a huge pool of internal fluids were spewing out of the wound. Of course, we got the wasp away to see if it was still saveable but from the looks of it, the damage had already been done and the caterpillar would soon bleed to death. Within a few hours after we took it back in, it died. 

To conclude, NEVER leave caterpillars (or other insects) unprotected outside if you have wasps roaming around your area, even for a few moments. 

- Brian

A few weeks ago we collected a few Monarch (Danaus plexippus) eggs since the species is so common this year, but now the caterpillars have all been killed by European Paper Wasps (Polistes dominula).

Back on 6/24 we decided to collect a few Monarch (Danaus plexippus) eggs just for the heck of it even though we were (and still are) bogged with tons and tons of various rearing projects this summer. The butterflies are so extremely abundant this year (a record high in over a decade according to some sources!) and finding eggs (or catching butterflies to lay eggs for you) is not a hard task. In just a half an hour we had collected 18 eggs without really even trying at all and brought them home to raise casually (more detailed in this post). But since then, we have gotten a bit lazy with them and decided to just stick them outside on our Tropical Milkweed (Asclepias curassavica) with in rearing sleeves. Big mistake. . .

Now, don't get me wrong here. Rearing sleeves for raising caterpillars outdoors on live plants is an excellent way to do it and is probably the best way that exists when looking for quality. It provides a lot of space and natural environment abd doesn't mess with their circadian rhythm. Most importantly, it provides much better sanitation and ventilation than most indoor rearing enclosures since caterpillars get to eat leaves fresh off the plant and don't have to swim in their own frass all day, decreasing the risk for disease outbreaks by a huge margin. So what exactly went wrong with our Monarch caterpillars? Well, as background information, the rearing sleeves were home-made out of window screening and clipped around the plant using clothespins. Not to say they were poorly designed, but they weren't terribly effective at keeping out small invertebrate predators.

The protective mechanisms of the sleeve is actually two-fold. The first line of defense is to conceal the area so that predators have a harder time detecting the caterpillars through vision. The second line of defense (if the first fails) is to create a physical barrier between the caterpillars and the predator. But in this case, the rearing sleeve failed to do either because we discovered that a whole bunch of European Paper Wasps (Polistes dominula) somehow managed to get their way into the rearing sleeve (don't ask us how they did it because the sleeve was shut tight on all sides with no openings at all that we knew of!). We caught them red-handed ripping apart the caterpillars and by today, only one Monarch caterpillar was left. Not to mention, a whole bunch of our Anise Swallowtail caterpillars (Papilio zelicaon) in rearing sleeves and some of our ovipositing females were also killed and eaten by the same wasps. 

The European Paper Wasps are incredibly intelligent. In fact, Hymenopterans (ants, bees, wasps, and sawflies) in general are arguably the most intelligent of all insects. The adult European Paper Wasp population exploded overnight one of these days when summer hit and now they are everywhere, searching on popular caterpillar host plants such as milkweed (Monarchs) and fennel (Anise Swallowtails). They clearly recognize that in our particular region, these plants are the most likely to have caterpillars and they search these almost exclusively over others; we also currently have Cecropia (Hyalophora cecropia) and Ceanothus (Hyalophora euryalus) outside in rearing sleeves on their respective host plants, and they have so far been completely untouched by the wasps who show no interest in them whatsoever. Once they hone in on their prey, they rip it up with their monstrous looking jaws and carry bits of the flesh away to their nest. The things are some of the hardiest insects out there and are extremely hard to kill. Today we tried crushing one with a rock but it was still alive and flew away even after being brutally smashed due to the fact that its head is so incredibly tough and unbreakable. 

Clearly, the best time to raise caterpillars outdoors is during the spring when the wasps are virtually nonexistent. Like stated earlier, they all of sudden came out of nowhere in huge numbers when summer started. Back in the spring when we put about fifty Anise Swallowtail caterpillars outside on the fennel without any rearing sleeve at all and not one was killed by predation. If we were to do that now, not one would be remaining within two days! 

Anyway, that is it for those Monarchs. It is not a terribly big loss since we weren't terribly into raising them in the first place when we first caught them. Even now we can always go back and collect more eggs since there are a whole bunch on our milkweed as of today. Plus, the butterflies still haven't disappeared, though they do seem to be a little less common than before. 

- Brian

Today, the 17 brachonid wasps that came out of our gray furcula larva (Furcula cinereoides​) have emerged.

The gray furcula moth larva (Furcula cinereoides) that we caught on 6/19 and turned out to be parasitized on 7/3. 17 unidentified species of parasitoid brachinoid wasp maggots bit their way and crawled out of the caterpillar to spin cocoons. These cocoons finally emerged today, just about a week later as we had predicted (the weakened caterpillar is still alive after all this time!). We had kept them just for the sake of seeing what the adults would look like for future reference and for identification purposes (we still have not identified them yet though) and immediately after they emerged, we threw them in the freezer to kill them. Of course we took some nice pictures of them though.

- Brian

- Brian

As the days past, we are discovering that more and more of our wild-caught Pipevine Swallowtail chrysalises (Battus philenor) had been parasitized by chalcid wasps (Brachymeria ovata). 

Anybody who has ever collected caterpillars or chrysalises from the wild has probably encountered a number of parasitoids. It is a risk we all have to take because you never know their there until its too late!

Starting on 6/26, we first noticed that two of our Pipevine Swallowtail (Battus philenor) chrysalises -- one directly wild-caught and the other from a fifth instar caterpillar that had been wild-caught -- had started developing strange red splotches on them. At the time, we were unsure whether this was normal or not since it was our first time really seeing Pipevine Swallowtail chrysalises at all. But what was alarming was that the red splotches were not symmetrical. Moreover, it also didn't make any sense that they would appear on some chrysalises and not others and that they showed up randomly and not immediately after the chrysalises had completely hardened after pupation. For example, the wild-caught one had clearly pupated for several days before we collected it because it was completely hardened (a process that takes at least two days) while the other one developed the spots immediately following pupation. 

In a few days, we confirmed our suspicions on 6/28 that something was up with these two chrysalises, as well as a with a third wild-caught one we found that day. The truth was, all three of the chrysalises seemed quite dead at that point so we thought it would okay to just pierce one open and investigate. Upon making an incision in the first wild-caught chrysalis with a pointy toothpick, we discovered that the chrysalis was, indeed, very much dead and hollowed out (eaten) by a very large parasitoid maggot. We later identified this as a species of chalcid wasp, specifically Brachymeria ovata. In the end, this was not a big surprise. I mean what else could have killed them besides simply drying out? 

In the past few days we are beginning to discover that many more of our recent chrysalises have been parasitized. Almost half of them at this point are highly suspect. Just like any other species of caterpillar, the Pipevine Swallowtails have their own natural enemies. Unlike most caterpillars, they don't have to worry about external predation because they are protected by their toxic aristolochic acids; parisitism is actually their biggest problem. The vast majority of the parasitized chrysalises have been undersized; none of the healthy ones are undersized. In hindsight, we were probably wrong about there being such a massive size variation in these species. Then again, the smaller ones do tend to be eaten alive faster and therefore show the red splotches much faster (some of the big chrysalises that seem healthy may still eventually turn out parasitized).

Luckily, we didn't actually have too many caterpillars/chrysalises that were wild-caught. The bulk of our stock right now comes from the 200+ eggs we have collected so hopefully all of the surviving members from these groups are totally fine. 

- Brian

Today we found out that the gray furcula larva (Furcula cinereoides) we found on 6/19 had been the host of some braconid wasp (Braconidae) maggots. What a lovely surprise. 

It has been 24 days since we first collected our first gray furcula larva on 6/19. When we first collected the little guy, it was only in second instar and in apolysis for third. For such a small caterpillar, we expected it to grow pretty fast. Though we had never had any experience with the species prior to finding it and did not know how many broods they have in our region, with the summer heat at 70+ degrees on most days we didn't expect it to take more than two weeks in the larval stage. But, of course we were wrong. 

By the 24th day, today, the little prominent still had only began feasting in the fourth instar for a few days. The caterpillar was very small, to say the least though we cannot say for sure that it was undersized. In any case, both slowed growth and being undersized are notorious symptoms of being parasitized.  And boy, was this caterpillar parasitized. This afternoon, we counted a total of 17 very fat braconid wasp larvae (family Braconidae) crawling out of its body and spinning their characteristic oval-shaped, white cocoons. Despite the warning signs, we simply had no idea. But then again, the parasitism rate can be alarmingly high among wild-caught caterpillars. 

After the maggots had chewed their way out of the exoskeleton to pupate, we didn't expect the poor prominent to have a trace of life left in it. But braconid wasps are actually quite different than tachinid flies (family Tachinidae) that we encounter more often. After they emerge from the host, the host is still very much alive (greatly weakened, but still alive) and brainwashed to defend the pupating maggots by thrashing around violently when disturbed. That's all our caterpillar is doomed to do for the rest of its short life before it finally does die when the wasps emerge from their cocoons about a week later. 

So that pretty much does it for Furcula cinereoides -- our only caterpillar has been busted. Probably won't be seeing it around here too much anymore unless we decide to take a few pics of the wasps when they come out.

- Brian

- Brian